Recursive file search

[mfschumann]

Pre-Submission checklist

• [x] There is no existing issue that already asks for this feature.
  
• [x] The feature already exists in rclone (on your PC or in Termux)
• [x] I am prepared to help make this feature

What version of Round-Sync are you using (About -> App version)?

2.1.4

What problem are you trying to solve?

I would like to be able to recursively search for files in all subdirs of the currently shown directory. Right now, only files in the directory itself are found. Depending on how the files are organized a recursive search would be a very welcome enhancement.

What should Round-Sync be able to do differently to help with this problem?

Include search results from all subdirs when entering text in the search bar. In order to get the results, one could either implement a recursion based on DirectoryObjects or call one of the rclone ls variants with an appropriate filter string and parse the result.