USe sheldon to load plugins and source extra commands

zsh/plugins/github-copilot.plugin.zsh

@@ -0,0 +1,10 @@
+#!/usr/bin/env zsh
+
+# Setup GitHub Copilot
+# first check we even have the genereic `gh` command
+if type gh > /dev/null; then
+  # Now check we have the copilot plugin installed with `gh`
+  if gh extension list | rg copilot -c > /dev/null; then
+    eval "$(gh copilot alias -- zsh)"
+  fi
+fi