Reloads the map source from its file.
NOTE: some map sources like the Map decoration and Highlight cannot be reloaded since they are not tied to a particular file on the disk. Generated map sources (for example using DownloadOsm (TODO)) need to be saved on the disk before trying to reload them (well, obviously).
reload-source [<source index>]
Reloads a map source under the index 3.
Reloads the last used map source.