[FEAT] Allow selection of directories/files from filesystem for annotation

[jsheunis]

A use case that is predicted to be common is as follows:

• A user has some data that they need to annotate
• They navigate to the view of the application that allows them to do this
• There is a button that says something to the extent of "Annotate data" or "Select data for annotation"
• Clicking the button should then open a file browser on their local system
• The user then selects a top-level directory or a file for annotation
• Upon selection, the file name(s) are available to the application and they are submitted to a function that turns them into RDF metadata using datalad-concepts-based schemas. This implies the need for a basic translation script from a directory tree (or file path) to what will likely be dldist:Distribution-based linked metadata.
• Once linked-metadata exists in the application, the user can inspect this and start annotating the "uploaded" files, i.e. start adding and/or linking more metadata.

There could be other entry points to this workflow to achieve the same results. For example, the script to generate basic linked metadata from a directory tree or files could already have been run on the files offline, and the user might just need to upload this metadata and start annotating it. This would be using the same standard functionality that allows a user to fetch RDF from a local file or from an online endpoint.

[jsheunis]

I took a first shot at this here: 1d67741