Func `call` only works for comptime values.

[somethingelseentirely]

It looks like Func.call can only be called with comptime known values. I'm not sure if this was missed because all the examples only use literals, or if the semantic of zig has changed recently.

Not being able to call functions with dynamic values makes calling them rather moot, so I'll see what I can do to fix this 😅

Code in question is here: https://github.com/zigwasm/wasm-zig/blob/8f9a0d1f7f53248f32272beb0b7b90061b8f3c30/src/main.zig#L170-L186