Add option `--do-not-add` to `sync-hooks-additional-dependencies`

[souliane]

Closes #8

Successful PR Checklist:

• [x] Tests
• [x] Documentation

PR label(s):

• [ ] https://github.com/ewjoachim/poetry-to-pre-commit/labels/breaking
• [x] https://github.com/ewjoachim/poetry-to-pre-commit/labels/feature
• [ ] https://github.com/ewjoachim/poetry-to-pre-commit/labels/bugfix
• [ ] https://github.com/ewjoachim/poetry-to-pre-commit/labels/miscellaneous
• [ ] https://github.com/ewjoachim/poetry-to-pre-commit/labels/dependencies
• [x] https://github.com/ewjoachim/poetry-to-pre-commit/labels/documentation