chore: include more justfile commands in ci

[mwpb]

Create a reusable workflow to setup our project environment and run a command. Use this for the existing checks and add two more checks.

• Check examples do not error
• Check docs do not error
• Also trigger a docs deploy on release so we don't have to do this manually.
• Remove quantinuum-sphinx because it is failing and we don't use it.

EDIT: GitHub is confused when I try to modify/delete ci.yml so I'm going to try this in two separate PRs... the next will remove the old ci.yml.

[johnchildren]

EDIT: GitHub is confused when I try to modify/delete ci.yml so I'm going to try this in two separate PRs... the next will remove the old ci.yml.

This is probably from the "required checks", we could disable it now if you like? But I guess we can turn the new ones on at the same time otherwise.