Replace constant `PHP_EOL` to `"\n"`

[vjik]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Fixed issues	#178

[what-the-diff[bot]]

PR Summary

• Added new class and method for HTML handling A new class has been introduced for HTML, which also contains a method to generate HTML. This will make it easier to create and manipulate HTML structures in our code.

• Standardizing line endings in Form.php The form file now uses a standardized line-ending format ("\n") which will make the code more consistent and less dependent on the platform-specific PHP_EOL constant.

• Updated unit tests in FormTest.php

  • The unit tests now conform to the new line-ending standard by using "\n" instead of PHP_EOL.
  • A new unit test has been added to validate the functionality of the "Stringable Csrf Token".
  • The tests for the default Csrf token have been updated. They now look for "_csrf" instead of "csrf-token", which aligns with the recent changes made to the Csrf token's default name.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (541494b) 100.00% compared to head (49a7499) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #179 +/- ## =========================================== Coverage 100.00% 100.00% Complexity 770 770 =========================================== Files 85 85 Lines 2078 2078 =========================================== Hits 2078 2078 ```

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