add open in app button to mod & modpack project pages

[evergales]

I noticed that theseus takes 'modrinth://' deeplinks for mods and modpacks

I thought it would be nice to add an 'open in app' button to those pages
because as far as I know there is currently no way (other than pasting code into console)
to use unlisted mods or modpacks in the launcher
and this could be a convenient way to make that a bit better
along with just being a nice qol feature

the-thing.mp4

I wasn't sure about making a thread for this in discord but can if needed!

[Prospector]

We had planned on implementing it a different way, but I think doing it this way would be great for now!

One thing is, this should work for anything except for a mod that only supports plugin loaders I believe, since the Modrinth App supports everything but plugins.

[evergales]

I think it should be correct now
but #1227 needs to be fixed
and I also think UrlConfirmModal is grabbing old project versions when installing
fixed in: theseus/#1228