feat: implement subject pattern

[jef]

Description

• Implements subject pattern; closes Introduce subject regex #253
• Updates tsconfig
• Updates UX

Testing

Updates some tests

New dependencies

• Bumps Node.js
• Uses vitest over jest
• Uses bare minimum eslint + prettier

[Copilot]

Pull Request Overview

This PR implements a subject pattern feature for conventional commit validation, allowing users to specify a regex pattern to validate the subject portion of pull request titles. The changes also modernize the codebase by migrating from Jest to Vitest, updating Node.js version, and switching to ES modules.

• Adds a new subject_pattern input parameter that accepts regex patterns for validating commit message subjects
• Modernizes the build system with ES modules, updated dependencies (Vitest, ESLint, Rollup), and Node.js 22
• Replaces external conventional-commit-types dependency with local implementation and improves GitHub token handling

Reviewed Changes

Copilot reviewed 19 out of 38 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/lint.ts	Implements subject pattern validation logic and updates import statements to ES modules
src/lint.test.ts	New comprehensive test file using Vitest with subject pattern test coverage
src/github.ts	Improves GitHub token handling with fallbacks and converts to ES module imports
src/conventional-commit-types.ts	New local implementation of conventional commit types replacing external dependency
package.json	Major dependency updates including Vitest, ESLint, and Node.js version bump to 22
action.yaml	Adds subject_pattern input and makes token optional with default value

Comments suppressed due to low confidence (1)

src/lint.ts:34

• The variable name matchedType is misleading as it stores a regex pattern, not the actual type. Consider renaming it to matchingRegex or foundMatch.

  const matchedType = matches.find((regex) => regex.test(title));