feat: allow for authenticating Steam users without official

[AnthonyFuller]

As title. Validates using the app ticket.

Pretty much done aside from the backend implementation (and final polish).

[AnthonyFuller]

Not a clue as to why merging from master causes esbuild to start failing...

[grappigegovert]

Looks good from a quick glance, but I don't see why you would hash the ownership ticket; isn't Map already implemented as a hash map internally?

[AnthonyFuller]

It is, the hash is more for a reference for when RDIL does the backend implementation so he knows what to hash.

[AnthonyFuller]

Okay, so updating node fixed esbuild failing. Good to know.
EDIT: Apparently not it just successfully built? Very confusing - I must've opened the previous run or something...

[AnthonyFuller]

I've removed the dependency on steam-appticket and added a util function to parse app tickets (it only parses a subset of the data - the parts we actually use).

Now we just need the backend implementation.

[AnthonyFuller]

Okay, this is basically done now - just requires the backend side of things to be finalised (one or two things to iron out, otherwise that's done too).

Reminder: update the default of steamAuthenticationMethod to BACKEND.