0.2.0 - AgentWorkflow

refactor: update version and refactor commit workflow

- Bump version from 0.1.0 to 0.2.0 in `__about__.py`.
- Refactor `commit.py` to use `llama_index.core.agent.workflow` instead of
`llama_index.core.workflow`.
- Replace `git` module with `tools` module for handling git operations.
- Remove `CommitFlow` and `CommitEvent` classes, replacing them with `commit_agent` using
`AgentWorkflow`.
- Delete `git.py` as its functionality is now integrated into the `tools` module.