Incorrect extra escaping of special characters

@zef This does not parse on edge build (but works in Lua 5.4+ command line):

```space-lua
function paragraphCount(text)
  return #(string.gmatch(text, '[\r\n][\r\n]+')) + 1
end
```

But this does parse - needs double backslashes to be satisfied (which means that it cannot work if parsed that way):

```space-lua
function paragraphCount(text)
  return #(string.gmatch(text, '[\\r\\n][\\r\\n]+')) + 1
end
```

The same for double quoted strings.

Should I create GH issue? Also see related case.

P.S. This is blocking issue for me. I am in the middle of rewritting some space script functions into Lua.