Allow to switch to other catalogs although a catalogUrl is defined

[m-mohr]

Sometimes it could be useful to be able to switch e.g. between a production and a testing/dev catalogs. STAC Browser already has the possibility to select data sources (from STAC Index), but it might also be a nice addition to be able to customize the list of catalogs shown there to a custom list and then to allow to switch to other catalogs although a catalogUrl is defined for the default rendering.

[m-mohr]

Here's how I'd imaging it: https://github.com/radiantearth/stac-browser/pull/380#issuecomment-2096190270