[Docs] Translate the migration/hook.md to English

[SheffieldCao]

Thanks for your contribution and we appreciate it a lot. The following instructions would make your pull request more healthy and more easily get feedback. If you do not understand some items, don't worry, just make the pull request and seek help from maintainers.

Motivation

Update docs: English version of migration/hook.md.

Modification

Add English version doc migration/hook.md.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMCls.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[CLAassistant]

All committers have signed the CLA.

[SheffieldCao]

Thank you! All the review suggestions from @zhouzaida & @HAOCHENYE are updated in the new commit. a7c48dc