Improve & document API available to custom scripts

[Le0Developer]

Describe the feature

Currently the documentation for custom scripts is lacking multiple things (like the context object the function is taking as first argument). Also some kind of SDK should be available for simple tasks like making a counter go up.

Use case

UX

Additional context

No response

[Le0Developer]

Idea: the handler function takes a ctx argument. This context has multiple helper functions:

• ctx.fs -> gives filesystem access to a directory in the sage directory (ls, write, read, rm) (will need native app update)
• ctx.count(name) -> atomically increments a counter with the name
• ctx.current -> current (partial) steam user (account id, username, password etc if available)