DOC: update contributing to pandas documentation
- [x] closes #48035
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

I removed the part in the [Committing your code](https://pandas.pydata.org/docs/development/contributing.html#id9) section where it is said that commit messages should include the number of the GitHub issue the commit is contributing towards. I updated the pull request template to include cross references so that it's more clear how people should make use of referencing GitHub issues.

I fixed the code snippet `git commit -m` which causes an error and updated the documentation to include both commit message versions, the one line commit message and the more detailed commit message that can be done with an editor. Let me know if you would like to keep both versions or would like further changes.

Additionally, I moved the section about the prefixes to the [Finally, make the pull request](https://pandas.pydata.org/docs/development/contributing.html#id12) section of the documentation. Let me know if the prefixes need to be updated. 

Thanks for your feedback! I addressed your comments. I previously added the line `- [ ] xref #xxxx (Replace xxxx with the Github issue number)` in `PULL_REQUEST_TEMPLATE.md` because sometimes a pull request contributes to an issue but doesn't close it such as here: https://github.com/pandas-dev/pandas/pull/44798. However, I understand your concerns and removed this line. Thanks @marenwestermann! 