Select correct nvim implementation

Dynamically detect if flatpak is installed. If not use native binary.

nvim.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+if [ "`which flatpak`" ]; then
+	flatpak run io.neovim.nvim $@ 2>/dev/null
+else
+	nvim $@
+fi