Tab-indented multiline-strings are turned into single-line strings

Input (note that every line starts with a single tab character):

```nix
	''
	  foo
	  bar
	''
```

Expected output:
```nix
''
  foo
  bar
''
```

Actual output:
```nix
"  foo\n  bar\n"
```

This can be disastrous: https://gitlab.com/Fuzen-py/configsreborn/-/blob/2a6b5aa5c8bee37cc13ab35d186b8fa604f62b2c/Snow/homeManager/programs/waybar/default.nix#L93-96