Migrate Stamen map tiles to Stadia

[Heistergand]

From Telegram IITC General Group:

"Stamen map tiles [...] don't work anymore because Stamen has been bought by Stadia, so now the raster tiles are hosted by Stadia.
There is a migration page that details how to make the shift easily, here:

https://docs.stadiamaps.com/guides/migrating-from-stamen-map-tiles/"

Todo

• find out if an API key is really needed (as they say on their website) and how to deal with it.
  • It might be necessary to add something (popup?) where the IITC users have to add their own free API key which they have to obtain from the map tiles provider on their own.
• translate URLs in code to stadia URLs
• update attribution texts
• add new tile plugin with new provider name in IITC
• set old tile plugin to deprecated (deleted folder)
• update IITC plugin website

[DanielOndiordna]

I have been creative today and I have made a new plugin for Stadia/Stamen maps:
https://softspot.nl/ingress/plugindetails/iitc-plugin-stadiamaps

Plugin description: Add the map layers and overlays from stadiamaps.com (Stadia, Stamen, Alidade). A personal API Key is required. Setup instructions are available in a dialog.

Using an API Key is mandatory.
It is okay if someone wants to use (all or parts of) my plugin to update the original Stamen maps plugin. But perhaps it is better to place my new plugin in the community plugins section.