[MOD] Mess a bit with rich replies, add XEPS-TBD

This should be a nice list of future XEPs to be implemented, so that I
can keep track of these without having to keep all of these in my head.

XEPS-TBD.TXT

@@ -0,0 +1,17 @@
+XEPs current supported are in src/XMPPThread.c, at the IQ disco advertising.
+
+For future XEPs:
+    - https://xmpp.org/extensions/xep-0444.html
+        This allows reactions, which Matrix also has support to. The two 
+        systems don't seem *too* restrictive on one-another (unlike some 
+        IM platforms I won't mention), so this doesn't sound too bad.
+    - https://xmpp.org/extensions/xep-0118.html
+        Informations on what a user is listening to. Matrix doesn't have 
+        good support for status, to be frank. Clients (including KappaChat) 
+        should consider having more support for those, rather than it being 
+        stuck as a FluffyChat/Nheko feature.
+        If any client devs hear this, please consider adding these, 
+        (especially if you're a smElement employee!)
+    - https://xmpp.org/extensions/xep-0084.html
+        Avatar support would be extremely useful, if just a QoL improvment.
+        Matrix and XMPP both have support for these.