Improve README a little;

README.md

@@ -1,4 +1,19 @@
 lovr-docs
 ===
 
-The documentation for [LÖVR](https://github.com/bjornbytes/lovr).
+This repository contains the documentation for [LÖVR](https://github.com/bjornbytes/lovr).
+
+There are three main types of documentation here:
+
+- The `api` folder contains a Lua table containing metadata for all LÖVR functions and objects.
+  - This is used to generate documentation, but is also useful for integrating with other tools
+    (e.g. autocomplete for the LÖVR API in text editors).
+- The `examples` folder contains sample LÖVR projects and tutorials.
+  - The ones listed in the `init.lua` file are shown on the website.
+  - All the code in the examples is released under CC0.  However, the models, textures, sounds, and
+    other assets used may use different licensing, so be sure to double check those.
+- The `guides` folder contains markdown files that explain LÖVR-related concepts in depth.
+  - Similarly, `init.lua` contains a manifest used to populate the sidebar on the website.
+
+There is a branch for each version of LÖVR.  Cherry picks are used to propagate fixes to the
+relevant versions.