Support computed property assignments

[Swatinem]

for (const name of ["a","b","c"]) {
    Foo.prototype[name] = function () {
    };
};

The anonymous function is resolved to the name Foo.prototype which is not quite correct. In this case best we could do is Foo.prototype[name].
In case the thing in brackets is a literal, we can also put that in there, if its a valid identifier, we can also convert it back to a "normal" property:

• Foo.prototype[1] -> Foo.prototype[1]
• Foo.prototype["not a valid ident"] -> Foo.prototype["not a valid ident"]
• Foo.prototype["valid_ident"] -> Foo.prototype.valid_ident