Add support for .repopackignore and enhance ignore pattern documentation

[yamadashy]

fix: #12
This pull request introduces support for .repopackignore files and improves the documentation for ignore patterns in Repopack.

Key changes:

• Added support for .repopackignore files
• Updated the "Ignore Patterns" section in the README
• Rearrange priority order for ignore patterns

Ignore priority order (from highest to lowest):

1. Custom patterns ignore.customPatterns
2. .repopackignore
3. .gitignore (if ignore.useGitignorePatterns is true)
4. Default patterns (if ignore.useDefaultPatterns is true)

[massdo]

Hello,

Thank you for your quick and thoughtful response! Your proposed approach sounds perfect and addresses the issue comprehensively.

I do have one small suggestion regarding the naming of the configuration option. Instead of useGitignorePatterns, perhaps useGitignore or useGitignoreFile would be clearer. This can help avoid potential confusion with a setting that might suggest switching from a wildcard format to a regex format.

Best regards,

[yamadashy]

Thank you for taking a look and for your suggestion! I agree that your proposed option is clearer.
I think we'll go with the simple useGitignore option.

[yamadashy]

I've implemented the changes. Your input has helped improve the feature!
I'm going to merge this pull request now. Thanks again for your contribution to making Repopack better!