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.

[timon-schelling]

This is actually not doing what is described in the discord message.

Hovering over layers in the layer panel should highlight their outline (specifically the shape outline in the viewport, not the layer itself in the panel)

Closing for now, feel free to open a new PR if you decide you want to give this another try.