Add logical AND-assignment and logical OR-Assignment

[juancarlospaco]

• Added logical AND-assignment and logical OR-Assignment for JavaScript targets.
• https://caniuse.com/mdn-javascript_operators_logical_and_assignment
• https://caniuse.com/mdn-javascript_operators_logical_or_assignment

[Araq]

Why? Nim programmers should write Nim code that we compile to JS, not JS code.

[juancarlospaco]

For interop purposes with the browser, it is useful for big heavy objects.
I mean there's emit for C targets and people don't go emit'ing whole modules.

[juancarlospaco]

@Araq Would you prefer to use a name like andAssign instead of &&= ? 🤔

[Araq]

No, I don't get the point at all, it's not about the name. Javascript uses + for string concats, should we also import its plus operator then? It just makes no sense...