Add highlight to layer outline on hover

[Tumypmyp]

Closes https://discord.com/channels/731730685944922173/881073965047636018/1383249080700108833

[Keavon]

I have force pushed this branch to move it to a new base. Ensure you have the branch checked out. Then run git stash on any local changes (and ask me before following these steps if you have any un-pushed commits on your local machine). Then fetch this branch and git reset --hard origin/highlight-layer-on-hover. And finally git stash pop your stashed local changes, if you stashed them.