Provide a publicly-editable list of Tutor plugins

[kdmccormick]

Context

This ticket is based on Regis's comment: #2 (comment)

Several plugins exist for Tutor and we expect many more to be made. We need a way for these to be discoverable.

Currently, the only list of officially supported plugins is from the overhang.io website: https://overhang.io/tutor/plugins
This list is linked to from here: https://docs.tutor.overhang.io/plugins.html#existing-plugins

Acceptance

Provide a publicly-editable list of plugins.

Regis suggests to add a table to the Tutor documentation listing all plugins. The table must include the following information:

• Name
• Short description
• Supported releases/tutor versions
• Link to project page (just a README, or something else?), which must include the following information:
  • Setup instructions
  • How to get support

When a plugin does not support the latest release, it would be moved to an "older plugins" table.

[kdmccormick]

Will be resolved by https://discuss.openedx.org/t/tutor-enhancement-proposal-tep-plugin-indices/8182