v0.1.7-alpha

feat: Generate commit message

- Added `commit` command to root command
- Added `commit` package with `commit` function that generates commit message and commits changes
- Removed `DiffFiles` function from `file` package
- Added `DiffFileContents` function to `file` package that returns the diff of two files
- Added `DiffStageAndHead` function to `file` package that returns the diff between the staged and committed changes
- Updated `code_review.yaml` with new `commit-summary` and `commit-label` prompts
- `commit-summary` prompt provides guidelines for summarizing a git diff
- `commit-label` prompt provides guidelines for generating a commit label and short message in {language}