Address multiple issues with comments and multiline tags

[50Wliu]

Requirements

• Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• All new code requires tests to ensure against regressions

Description of the Change

There are three issues addressed in this pull request.

1. Comments would be ignored in all parts of a multiline block, including the tag definition itself. language-yaml now tokenizes comments following a tag definition.
2. Multiline tag definitions would override the comment pattern, resulting in a comment receiving incorrect tag highlighting. The multiline tag definition regexes have been tweaked to match other similar regexes.
3. Key-like structures in multiline blocks would be tokenized as actual key structures rather than a continuation of the string block. The end regex has been changed to better match the spec.

Alternate Designs

None.

Benefits

Comment + multiline tag interactions will be improved.

Possible Drawbacks

These regexes just got a whole lot uglier. I didn't even think that was possible.

Applicable Issues

Fixes #84 Fixes #92

[Nixinova]

This PR introduced errors with valid hash signs in key names like this:

TXT: text
C#: programming

See #114