Add comments

Currently there is no comment support. This should be implemented as it is quite useful to comment the code.

This means that stuff like this should work:
```asm
mov rax, 0 ; Moves 0 into rax
; And this is a comment without any instruction
```

And also other types of syntaxes for comments should be possible. So characters like `#` should also be able to be used as single-line comments.