Improve book and migration guide page editing / feedback process

As it stands the only indication that someone can edit a page to improve it is an `Improve this page` link at the bottom of the page where it can easily be missed. These pages also lack a way to simply suggest, or give feedback, on the page without requiring the user to know how fix the issue themself. So the two things that are needed for this issue to be solved is:

1. Add a `Give feedback on how we can improve this page` link that opens up a new issue on the `bevy-website` repository for the user to put their feedback. (We should probably get issue templates to be used for this at some point).
2. Move the `Improve this page` (perhaps also change it to `Edit this page` for clarity) to a more visible place. One suggestion has been to the sidebar menu. (The feedback link should also be moved with the edit link as well).

Originated on Discord: https://discord.com/channels/691052431525675048/743559241461399582/1211733291951063050

Start by locating the page template that renders the existing `Improve this page` link in the bevy-website repository, then inspect how the sidebar menu and external issue links are assembled. The work is done when book and migration guide pages expose both edit and feedback links in a more visible shared location, with feedback opening a new issue in bevy-website.

Written by the indexing model from the issue text.