Controller support doesn't work

[tooda02]

Is your feature request related to a problem? Please describe.
Facepunch current support for Steam Input is incomplete, and it is not possible to implement controller support for a game using it. For example, it's missing Init() (required to set up Steam Input); gamepad text input support (required for Steam Deck certification); any way of retrieving all origins associated with an action; and several other important functions.

Describe the solution you'd like
Add several new methods to SteamInput

Additional context
See Pull Request #757 for a list of the proposed new methods. I've implemented these in my fork and verified them in my published game Stinky and Loof in Wonderland.