Setup presubmit for dart_skills_lint

[reidbaker]

Fixes #63

Blocked by #66

Linting for skills/ is done only on one machine.
dart test is run on linux/windows/mac so that the integration tests can run on each platform.

• Setup pre commit linting, formatting, analyzing

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

[gemini-code-assist]

Code Review

This pull request primarily focuses on minor cleanup, including fixing typos in documentation, removing trailing whitespace, and adjusting formatting in tests. It also enables the check-absolute-paths rule in the dart_skills_lint.yaml configuration. Feedback indicates that the implementation of this new rule is currently incomplete, as it lacks the necessary CLI flag registration and logic in the entry point to be fully functional and consistent with existing rules. Additionally, there are naming inconsistencies between the rule names used in the code and those documented in the README.