Add unpolished map tile generation script

[aquacluck]

This takes manual intervention but it does work. Possible improvements:

• Pure python would be nice for the starting section, just one lang
• Take romfs and tx tmp as docker volumes, prompt and wait for switch-toolbox extraction
• Prompt+skip saving fullsize maps, they're neat to have so I assumed people will want them

Full transparency, I don't really plan on further improving this. It'll be a one-time process for most people, and I'd need to figure out how to extract bntx from python to improve the experience very much.

I'm hoping this can be merged as documentation + 80% implementation regardless, since the process isn't documented at all today afaik

[savage13]

For reference: The original tiles were pasted together, reduced from 32000 to 24000 in width then the tiles were generated using a modified version of gdal2tiles. The merged files and tiles are quite large.

https://github.com/commenthol/gdal2tiles-leaflet