[feature request] share folder content (recursive) instead of folder-name

In MaterialFiles you can select one or more files and share them to other apps (i.e. send via bluetooth or via email)

When "the share" contains a directory-entry the share-consuming-app only gets the folder alias of the used FileProvider which cannot be processed further because FileProvider does not support browsing folders (see comment in https://stackoverflow.com/questions/48062097/how-to-open-a-directoryfolder-in-android-using-file-provider ).

As a result the share-consuming-app may crash (see MaterialFiles#575 or ToGoZip#28)

Instead of sharing the selected folder name share all files that are inside the folder (recursivly)

Example: (current working)

In MaterialFiles select the folder "sd_sub_test" and press "share"
MaterialFiles shares "sd_sub_test" with mimetype="vnd.android.document/directory"

requested change:

MaterialFiles shares all files inside the folder "sd_sub_test" (i.e. "sd_sub_test/test.txt", "sd_sub_test/Image.png") instead of sharing the folder name

Start by tracing MaterialFiles' current share flow for selected directory entries and how Android FileProvider produces the shared URI and MIME type. Verify the behavior with a folder containing nested files, then confirm that sharing the folder exposes all files recursively rather than only the folder alias.