Add "Conflicts" metadata

[nilFinx]

Marking certain packages as "it will conflict". Loaded at the same time, "You should use this, not this", etc.

[Bilal2453]

I am not sure I fully understand this idea, more specifically, in which scenario would this happen? why would packages conflict?

[nilFinx]

Something like proviing multiple package with the same file name, as you wouldn't use the original weblit aloglngside a fork of it.