module: add :tools collab

Add a collaborative editing module, powered by crdt.el.

Ref: https://code.librehq.com/qhong/crdt.el
Co-authored-by: Arte Ebrahimi <arteebrahimi@gmail.com>

templates/init.example.el

@@ -87,6 +87,7 @@
        :tools
        ;;ansible
        ;;biblio            ; Writes a PhD for you (citation needed)
+       ;;collab            ; buffers with friends
        ;;debugger          ; FIXME stepping through code, to help you add bugs
        ;;direnv
        ;;docker