docs: add migration guide

[M0NsTeRRR]

Description

add migration guide

[github-actions]

This pull request has merge conflicts. Please resolve the conflicts so the PR can be successfully reviewed and merged.

[Gylesie]

This guide is low value for users with existing Jellyseerr and Overserr instances. It essentially tells them to scratch whatever they had previously in e.g. docker compose and replace it with whatever is in the general getting started guide which is geared towards new users.

[M0NsTeRRR]

This guide is low value for users with existing Jellyseerr and Overserr instances. It essentially tells them to scratch whatever they had previously in e.g. docker compose and replace it with whatever is in the general getting started guide which is geared towards new users.

1. It’s still in draft, I need to confirm whether additional migration steps are required.
2. This is for users with less experience, and it’s meant to prevent support tickets like, 'Is it really as easy as updating the Docker image reference?' This way, we can simply redirect them here. Users with more experience already know how to handle the new image and what it does for them.

[Gylesie]

I understand its in draft, but you requested a review. So thats why I wanted to give some feedback.

I just dont find it helpful overall. It literally says to replace the whole compose file with new one. But there is a good chance that the user is running different services in a single compose file. What should they do then?

I dont think majority of users would need this much hand holding to migrate. Showing an example of an old docker compose file and then the new one with specific changes that were made highlighted would be better.

[gauthier-th]

LGTM