Make some/all input types readonly? (dict members, arrays, tuples)

[kainino0x]

This way if an application holds a readonly type it can pass it into WebGPU without having to cast it to writable.

[kainino0x]

Looking at this again, realizing it should apply to all of the dictionary members too, not just arrays.

[kainino0x]

In practice this is not very much of a problem because TypeScript is extremely lax about readonly enforcement and allows implicit conversion from readonly to writable in a lot of cases. I'm not even aware of warnings or lint options that make it stricter.