Explain how to export godot patches, mods and DLCs

**Your Godot version:**

3.2.3

**Issue description:**

This documentionation page https://docs.godotengine.org/en/stable/getting_started/workflow/export/exporting_pcks.html says the following "This tutorial should illustrate how easy adding mods, patches or DLC to a game is" while doing none of it.

After reading this page I am none wiser on how to add a patch to may game, how to create a mod nor how to make a DLC. It's the most brief page ever that simply describes how to export a pck file and nothing else. The instructions here don't explain anything beyond the most basic export.

**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/stable/getting_started/workflow/export/exporting_pcks.html