Add recipe for installing latest Neovim from appimage

This will download and add the latest Neovim appimage to the user bin dir,
or, if appimage can't be run, will extract the filesystem and add it to
~/.local paths.

recipes/default/neovim_appimage

@@ -0,0 +1,15 @@
+#! /bin/bash
+
+set -e
+
+cd "$TMP"
+
+curl -LO https://github.com/neovim/neovim/releases/latest/download/nvim.appimage
+chmod +x nvim.appimage
+if ./nvim.appimage --version ;then
+    mv nvim.appimage ~/bin/nvim
+else
+    ./nvim.appimage --appimage-extract
+    mv ./squashfs-root ~/.local/lib/neovim_squashfs
+    ln -s ~/.local/lib/neovim_squashfs/AppRun ~/.local/bin/nvim
+fi