impr: Better error message for mismatched attribute type

(After merging #1113)

const foo = d.interpolate('flat', d.location(0, d.mat4x4f));

This snippet produces the following error:

No overload matches this call.
  Overload 1 of 2, '(interpolationType: "perspective" | "linear" | "perspective, center" | "perspective, centroid" | "perspective, sample" | "linear, center" | "linear, centroid" | "linear, sample", data: PerspectiveOrLinearInterpolatableData | Decorated<...>): Decorated<...>', gave the following error.
    Argument of type '"flat"' is not assignable to parameter of type '"perspective" | "linear" | "perspective, center" | "perspective, centroid" | "perspective, sample" | "linear, center" | "linear, centroid" | "linear, sample"'.
  Overload 2 of 2, '(interpolationType: "flat", data: FlatInterpolatableData | Decorated<FlatInterpolatableData, unknown[]>): Decorated<FlatInterpolatableData, [...] | [...]>', gave the following error.
    Argument of type 'Decorated<Mat4x4f, [Location<0>]>' is not assignable to parameter of type 'FlatInterpolatableData | Decorated<FlatInterpolatableData, unknown[]>'.
      Type 'Decorated<Mat4x4f, [Location<0>]>' is not assignable to type 'Decorated<FlatInterpolatableData, unknown[]>'.
        Type 'Mat4x4f' is not assignable to type 'FlatInterpolatableData'.
          Type 'Mat4x4f' is not assignable to type 'F32'.
            Types of property 'type' are incompatible.
              Type '"mat4x4f"' is not assignable to type '"f32"'.ts(2769)
attributes.ts(255, 17): The call would have succeeded against this implementation, but implementation signatures of overloads are not externally visible.