Updating pseudo-classes to add defined, focus-visible and placeholder-shown

[cssinate]

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

Similar to #173 , this PR includes changes that were added to octref/language-css

This time, three pseudo-classes were added: defined, focus-visible, and placeholder-shown

Alternate Designs

Benefits

Adds more recent pseudo-classes

Possible Drawbacks

Nothing major

Applicable Issues

https://github.com/microsoft/vscode/issues/115480

[cssinate]

Seems this work is done in #141