Allow quotes inside of unquoted keys

[deckar01]

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

Allow quotes inside and after a key if it does not start with a quote.

Alternate Designs

The grammar was explicitly performing additional, incorrect behavior, so removing this behavior was the only solution.

Benefits

Compliance with the YAML spec for keys and correct syntax highlighting of keys.

Possible Drawbacks

None.

Applicable Issues

Closes #83

[winstliu]

:zap: Thanks for the extra specs!