Fix linebreaks when importing strings

[Chesyon]

Fixes #812. When exporting strings to a CSV, actual linebreaks are swapped for \n, as shown here:

wr.writerows([[x.replace("\n", "\\n")] for x in self._str.strings])

The issue arises from the fact that this is not undone when importing, meaning the linebreaks stay as \n instead of actual linebreaks. This can be undone by adding a replace("\\n", "\n") to the code relevant to importing, causing the new code to look like this:

strings.append(row[0].replace("\\n", "\n"))

This should cause linebreaks to be imported properly instead of as \n.

I'm unable to build SkyTemple to see if this works myself, but I'm hoping my logic makes sense.

[Frostbyte0x70]

The fix works, at least on Windows.