Add lowercase directives followup

[richardm90]

Changes

Followup to PR #283.

1. Removed the UppercaseDirectives linter option from the code base.
2. Fixed the use of the new DirectiveCase linter option. Most references used DirectiveCasing, now all references use DirectiveCase.

Checklist

• [x] have tested my change
• [ ] updated relevant documentation
• [x] Remove any/all console.logs I added
• [x] eslint is not complaining
• [x] have added myself to the contributors' list in the README
• [ ] for feature PRs: PR only includes one feature enhancement.

[worksofliam]

@richardm90 Sorry my friend - any chance you can fix the conflicts here? I switched out our ugly test suite for a brand new one using vitest, which works across all platforms now!

[richardm90]

Fix conflicts please!

Will do.

[richardm90]

Fixed conflicts