Add Emacs desktop provisioning and dev toolchain packages

Install Emacs and copy the desktop .emacs.d config so the editor setup is managed with the rest of desktop dotfiles. Add vterm/build/debug dependencies plus C/C++ and Go tooling needed by the configured workflow.

dotfiles/desktop/.emacs.d/snippets/sh-mode/help

@@ -0,0 +1,19 @@
+#name : help
+# --
+_show_help() {
+  cat <<EOF
+NAME
+   $(basename "\$0")
+
+SYNOPSIS
+   $(basename "\$0")
+
+OPTIONS
+  --help Don't panic
+
+AUTHORS
+     skybert wrote the initial version.
+
+$0
+EOF
+}