Add Basemap plus BGS and other map layers on creation of GeoPackage

[Didymograptus]

Proposal: Allow the user to add a base map and/or WMS BGS maps (e.g. Bedrock, boreholes etc) to the project when creating the GeoPackage from the AGS file.
Benefit: Provides immediate visual context to the user, without the user having to understand how to import WMS layers.