Docs: explain how to disable doctool hotkeys that interfere with ours

[humitos]

Comes from #25 (comment)

We want to document:

• How to disable keyboard shortcuts on MkDocs (https://squidfunk.github.io/mkdocs-material/setup/setting-up-navigation/#keyboard-shortcuts)
• How to disable / keyboard shortcut on Sphinx (https://www.sphinx-doc.org/en/master/usage/theming.html#builtin-themes)

[humitos]

Another user is reporting the same issue in Material for MkDocs: squidfunk/mkdocs-material#6652

[humitos]

There is a new release of Material for MkDocs, v9.5.5, that should help with the issue.

[humitos]

I tested it in https://test-builds.readthedocs.io/en/mkdocs-material/ and I wasn't able to reproduce the issue. You can open the search as-you-type and write next or previous and it does not interfere with MkDocs hotkeys anymore 🎉