feat: Allow ignoring files, support config file

[doomspork]

Across our repos we have a need to ignore certain files:

• In the JSON API repo we should ignore the .formatter.exs changes for now until we sort out how to handle those edge cases.
• In our elixir-companies repo we need to ignore all of release-please.

[Copilot]

Pull request overview

This PR adds support for ignoring specific files during sync operations and introduces a configuration file mechanism to manage sync settings. The implementation allows users to specify ignore patterns either via action inputs or a YAML configuration file, with action inputs taking precedence over file-based configuration.

Key changes:

• Added file ignoring functionality with glob pattern support using minimatch
• Implemented configuration file loading from .github/actions-sync.yml (customizable path)
• Extended the Config type with ignoreFiles and configFilePath fields

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 12 comments.

Show a summary per file

File	Description
src/templates.ts	Adds shouldIgnoreFile function and filtering logic to skip files matching ignore patterns
src/templates.test.ts	Adds tests for exact match, glob pattern, and multiple pattern file ignoring scenarios
src/index.ts	Integrates config file loading into the main workflow
src/configFile.ts	Implements YAML config file parsing and merging with action inputs
src/configFile.test.ts	Comprehensive tests for config file loading, precedence rules, and error handling
src/config.ts	Extends Config type and adds configFilePath and ignoreFiles input retrieval
package.json	Adds dependencies for js-yaml and minimatch libraries
action.yml	Adds config-file and ignore-files input definitions

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