Add deprecation notice and Blender compatibility notice to README

README.md

@@ -4,11 +4,28 @@ Enhanced Collada exporter for [Blender](https://www.blender.org), making the
 format viable for importing meshes into game engines such as
 [Godot Engine](https://godotengine.org) using a libre format.
 
+___
+
+**Warning:** This add-on is no longer maintained. With the rise of glTF 2.0,
+Collada has been getting less traction lately. If you need a full-featured
+import-export pipeline, **consider using glTF 2.0 instead**.
+(The glTF 2.0 exporter is built into Blender.)
+
+Pull requests may still be merged, but no guarantees are made as for this
+add-on's viability.
+
+**Blender compatibility:** The current `master` branch requires at least Blender
+2.80. The last commit with Blender 2.79 support is
+[`9a8fae9`](https://github.com/godotengine/collada-exporter/commit/9a8fae951fe76209a7bb6c6cbc692478585283b8).
+If you need to use this add-on with Blender 2.79,
+[download a ZIP of that commit](https://github.com/godotengine/collada-exporter/archive/9a8fae951fe76209a7bb6c6cbc692478585283b8.zip)
+(this old version is not compatible with Blender 2.80 or later).
+
 ## Installation
 
-1. Copy the `io_scene_dae` directory the location where Blender stores the
+1. Copy the `io_scene_dae/` directory the location where Blender stores the
    scripts/addons folder on your system (you should see other io_scene_*
-   folders there from other addons). Copy the entire dir and not just its
+   folders there from other addons). Copy the entire directory and not just its
    contents.
 2. Go to the Blender settings and enable the "Better Collada Exporter" plugin.
 3. Enjoy full-featured Collada export.