Base maps: Support web map serivces

[annehaley]

The construction of a tile url for a WMS source is different than typical XYZ tiles.
Maplibre example here: https://github.com/BryonLewis/vue-maplibre-compare/blob/main/demo/src/DemoMapCompare.vue#L47-L67

After resolving #240, another iteration should add support for web map service base layers.