Feedback for upload-source endpoint

[shabnomnom]

It would be helpful to have the upload-source endpoint, automatically call the list-source endpoint to list all the already existing sources for the tileset ID before moving to add or replace the source. That way users can compare source sizes and avoid duplicating a source that already exists in their tileset. So it will be something like:

tilesets upload-source <username> <id> ./file.geojson
“The following source exists in tileset if you want to replace your source use --replace flag. If you want to add an additional source enter, "Yes". Enter "No" to continue with the existing sources”
List of the sources here...