passing vm-specific configs

[satrobit]

Hey,
I'm trying to add "fuel" to the wasmtime engine used here, but there's apparently no way to pass engine configs. It'd be nice to have them. I can work on it if you accept contributions :)

[spacewander]

PR is welcome!

[spacewander]

Could you show us your API design before coding in it?

[satrobit]

Sure. I'll send the design before I start coding it.