add list-files command

[kaloyan13]

Add a list-files command, with optional JSON output.

$ mergin list-files mergin/simplebees

Usage: mergin list-files [OPTIONS] PROJECT

  List files in a project.

Options:
  --json  Output in JSON format
  --help      Show this message and exit.

$ mergin list-projects
List of projects (all public):
Fetched 9 projects .
  mergin / pgv                            	   0.1 MB	v6
  mergin / databank                       	   0.7 MB	v7

$ mergin list-files mergin/databank
Fetched 8 files .
  databank.qgz                            	   0.0 MB
  Survey_points.gpkg                      	   0.1 MB
  datas/2-Survey_points.gpkg              	   0.1 MB
  datas/0-Survey_points.gpkg              	   0.1 MB
  datas/3-Survey_points.gpkg              	   0.1 MB
  datas/4-Survey_points.gpkg              	   0.1 MB
  datas/7-Survey_points.gpkg              	   0.1 MB
  datas/8-Survey_points.gpkg              	   0.1 MB

$ mergin list-files --json mergin/databank
[{'checksum': 'fc111bd14304993eb689dd76e8f0f68694a87388', 'mtime': '2024-03-21T17:56:30.061676Z', 'path': 'databank.qgz', 'size': 15391}, {'checksum': '8fc64b4ae99fa6ae2a572672b2fb38cae42604c7', 'diff': {'checksum': 'ff8a361f3d933049940e08783d1943f662fd126d', 'mtime': '2024-03-21T19:56:28.516560+02:00', 'path': 'Survey_points.gpkg-diff-a50c162b-ddcc-400a-a8c1-bd1fde7eed56', 'size': 220}, 'mtime': '2024-03-21T17:56:30.061677Z', 'path': 'Survey_points.gpkg', 'size': 98304}, {'checksum': '26bf84f140bf7df97eee8a589cc2fbe47f3a766d', 'mtime': '2024-03-21T17:45:36.624145Z', 'path': 'datas/2-Survey_points.gpkg', 'size': 98304}, {'checksum': '26bf84f140bf7df97eee8a589cc2fbe47f3a766d', 'mtime': '2024-03-21T17:47:41.844995Z', 'path': 'datas/0-Survey_points.gpkg', 'size': 98304}, {'checksum': '862b7c799f588f2aa0ddf4ef8403c194c91c91ae', 'mtime': '2024-03-21T17:49:21.581621Z', 'path': 'datas/3-Survey_points.gpkg', 'size': 98304}, {'checksum': '07b886469eb209534813d11c01b726a334d49066', 'mtime': '2024-03-21T17:50:50.668199Z', 'path': 'datas/4-Survey_points.gpkg', 'size': 98304}, {'checksum': '3709214406a591629e83d296f8c67c06c8dd4cd2', 'mtime': '2024-03-21T17:51:59.117511Z', 'path': 'datas/7-Survey_points.gpkg', 'size': 98304}, {'checksum': '1220866c3618b30c013d55a7f1cbe9be60e40e1f', 'mtime': '2024-03-21T17:56:30.061670Z', 'path': 'datas/8-Survey_points.gpkg', 'size': 98304}]

[MarcelGeo]

Hello @kaloyan13 . Thank you very much for your contribution. I apologize for the delayed response.
If you're still able to work on this pull request, I have a few minor suggestions:

• could you rename fmt_json to json?
• you can remove namespace argument (we can make unique interface with share, where namespace/project_name is passed directly to project param)
• could you give examples of results to PR?
• Add command to README.md

[MarcelGeo]

Thanks @kaloyan13 , feel free to make any other contributions. 🔥 In the future, try to use black.