Adding popup to specify new user path if default one fails

[Wires77]

Fixes #7431 .

Description of the problem being solved:

This requires PathOfBuildingCommunity/PathOfBuilding-SimpleGraphic#46 to function, and adds a workaround for users who have unicode characters in their default user path.

Still TODO:

• Find a better way to check for a valid path
• Implement loading settings and shared items after saving
• Restore dev code loading settings from script path (currently always loading from user path for testing)
• Add a link to a workaround document to prevent this from appearing every time

Screenshot and behaviour

• Popup cannot be closed without specifying a new path
• Popup opens on startup every time until fixing their Documents path to not contain unicode
• Sanitizes input, only allowing Save to be clicked once it contains no ? characters (PoB's unicode representation)
• Save button will load settings.xml and everything else from that path
• Question mark button leads to https://github.com/PathOfBuildingCommunity/PathOfBuilding/wiki/Why-do-I-have-to-change-my-Settings-path%3F

To Test

Do the opposite of the workaround in this comment and set your Documents path to something with Cyrillic characters in it (e.g. Документи ): #7431 (comment)
You'll also have to comment out the if launch.devMode or (GetScriptPath() [...] conditional section on line 76 of src/Main.lua, otherwise the GetUserPath() function won't even get called.