Minor fixes and improvements

[vjik]

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	❌
Fixed issues	-

[what-the-diff[bot]]

• Fix typo in exception message that throws on invalid buttons data in ButtonGroup widget
• Add typehint for $value parameter of input() method to allow null values and make it more strict (allow only bool, float, int or string)
• Make all methods return static instead of self so they can be chained with each other without casting result to the same class as original object was created from
• Remove self return type from all methods.
• Change method parameters to be typed with nullable types where possible (e.g., string|null instead of ?string).
• Add static keyword for class instantiation in some classes, e.g.: NormalTag::tag() -> new self(). This is not done everywhere because it's a breaking change and we don't want to break the API at this point in time as there are many users relying on these APIs already without having PHP 8 installed yet or even knowing about its existence :) . We will do that later when more people have upgraded their projects to use PHP 8 so they can benefit from the performance improvements provided by using static calls over dynamic ones: https://wiki-dev1/php8#static_calls_vs._dynamic_calls .
• Fix type hinting for Input::hidden, Input::text, etc.
• Add missing return types to some methods in Tag classes (Input/File, Range).
• Remove unnecessary casts from CheckboxList and RadioList widgets: $value === null ? null : (string)$value; -> $value === null ? null : (string) $value;
• Fixed typo in exception message
• Added missing typehint for $value parameter of Select::values() method
• Removed unused import statement from MediaTagTest class and fixed fallback test case to use correct assertion instead of expecting an exception (which is not the right way to check if a tag renders correctly)

[codecov[bot]]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage :thumbsup:

Coverage data is based on head (495e969) compared to base (d4f08cc). Patch coverage: 100.00% of modified lines in pull request are covered.

:exclamation: Current head 495e969 differs from pull request most recent head d0f1f5f. Consider uploading reports for the commit d0f1f5f to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #143 +/- ## =========================================== Coverage 100.00% 100.00% + Complexity 755 750 -5 =========================================== Files 83 83 Lines 1964 1957 -7 =========================================== - Hits 1964 1957 -7 ``` | [Impacted Files](https://codecov.io/gh/yiisoft/html/pull/143?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft) | Coverage Δ | | |---|---|---| | [src/Tag/Table.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9UYWJsZS5waHA=) | `100.00% <ø> (ø)` | | | [src/Html.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL0h0bWwucGhw) | `100.00% <100.00%> (ø)` | | | [src/Tag/Base/BooleanInputTag.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9CYXNlL0Jvb2xlYW5JbnB1dFRhZy5waHA=) | `100.00% <100.00%> (ø)` | | | [src/Tag/Base/InputTag.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9CYXNlL0lucHV0VGFnLnBocA==) | `100.00% <100.00%> (ø)` | | | [src/Tag/Base/ListTag.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9CYXNlL0xpc3RUYWcucGhw) | `100.00% <100.00%> (ø)` | | | [src/Tag/Base/MediaTag.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9CYXNlL01lZGlhVGFnLnBocA==) | `100.00% <100.00%> (ø)` | | | [src/Tag/Base/NormalTag.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9CYXNlL05vcm1hbFRhZy5waHA=) | `100.00% <100.00%> (ø)` | | | [src/Tag/Base/TableCellTag.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9CYXNlL1RhYmxlQ2VsbFRhZy5waHA=) | `100.00% <100.00%> (ø)` | | | [src/Tag/Base/TableRowsContainerTag.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9CYXNlL1RhYmxlUm93c0NvbnRhaW5lclRhZy5waHA=) | `100.00% <100.00%> (ø)` | | | [src/Tag/Base/Tag.php](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft#diff-c3JjL1RhZy9CYXNlL1RhZy5waHA=) | `100.00% <100.00%> (ø)` | | | ... and [18 more](https://codecov.io/gh/yiisoft/html/pull/143/diff?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=yiisoft)

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