[no-unsafe-mutable-readonly-assignment] add fixer

[danielnixon]

For examples where the RHS is an array or object literal we should be able to automatically fix by appending as const.

Example:

const foo: ReadonlyArray<string> = ["foo"];

Should be automatically fixable to this:

const foo: ReadonlyArray<string> = ["foo"] as const;

[danielnixon]

This fixer would only work if all properties on LHS are readonly, recursively. Otherwise the as const RHS after fixing would fall afoul of the inverse rule: unsafe readonly -> mutable assignment.

We should be able to detect that and only enable the fixer when the LHS in entirely readonly.