Add maintenance schedule

**Describe the feature request**:
We should consider implementing a regular maintenance schedule to SecLists. Currently, every year we have to:
- Add a new "Most used passwords of the year" wordlist
- Add new years to the wordlists that rely on the current year
- Update the github actions dependency SHA hashes (See: #1297)
- Verify relevance of existing wordlists. There exist a number of wordlists within SecLists that may or may not be worth keeping in the repository considering their relevance to the modern world. Every year we should consider which wordlists should be moved to a directory of deprecated wordlists, and which should be deleted. See, for example: [Discovery/Web-Content/LEGACY-SERVICES
](https://github.com/danielmiessler/SecLists/tree/master/Discovery/Web-Content/LEGACY-SERVICES)

This could all be in a file named "MAINTENANCE-POLICY.md". Preferably with more detail than what is described here, like the filepath locations of all the wordlists that need to be updated, filepaths of the github actions that need to be updated, links, shorthand commands, etc.

- [X] I intend to open a pull request later