clearer errors

Right now it's a bit devex unfriendly if you use a non `js` wrapped value as an arg to a function signature. For example:

```
pub fn foo(self: *const Bar, my_bool: bool) !void { ... }
```

The error, when you try to build:

```
➜ zig build build-lib:bindings
build-lib:bindings
└─ install bindings
└─ compile lib bindings Debug native 1 errors
zig-pkg/zapi-2.2.0-rIqzUXBaBADUsvvvB2N5kOBdLEO0rGPhowTqmIXe3qVh/src/js/wrap_function.zig:180:5: error: convertArg: unsupported type bool
@compileError("convertArg: unsupported type " ++ @typeName(T));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

it does not tell you exactly where/what went wrong, but only something internally that went wrong, and unless you're familiar with `zapi` the error can be quite confusing.