modify `navigate-pages-with-arrow-keys` to match GitHub's `n` / `p` keys #4742

Description

from https://github.com/sindresorhus/refined-github/pull/4691#issuecomment-907578663

I think n/p has existed for a while actually. It might make more sense to change our feature to match n/p in order to extend it to more pages. Arrows feel wrong accessibility-wise.

While I agree with the change, I did a quick test to check whether the change was feasible. p is used as a hotkey for the Project filter on issues and pull request lists. I feel that the hotkey is most used on the issues and pull request lists.

Here are 2 options that I could think of ( both after modifying the feature to match GitHub's choice of n / p across all other supported pages ) :

1. Maintain the arrow keys functionality for issues and pull request lists.
2. Drop the feature for issues and pull request lists

Either way, there is going to be a feature rename and migration that would be required.

Example URLs

• Issue list : https://github.com/sindresorhus/refined-github/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc
• Pull request list : https://github.com/sindresorhus/refined-github/pulls?q=is%3Apr+sort%3Aupdated-desc+is%3Aclosed
• Search page : https://github.com/sindresorhus/refined-github/search?q=navigat
• Commits Page :
  • https://github.com/sindresorhus/refined-github/commits/main/source/features/navigate-pages-with-arrow-keys.tsx
  • https://github.com/sindresorhus/refined-github/commits/main
• Releases Page : https://github.com/sindresorhus/refined-github/releases
• Notifications Page : https://github.com/notifications
• Pull Request Commits :
  • d9621aa (#4699)
  • dc04365 (#4699)