add solanum.chat/reply capability

_spec/reply.rst

@@ -0,0 +1,29 @@
+---
+title: reply
+alias:
+  - reply
+---
+
+Description
+===========
+
+The ``solanum.chat/reply`` capability informs the server that you'd like to be in receipt of IRCv3's `reply message tag <https://ircv3.net/specs/client-tags/reply>`_, so that the server will not attempt to downgrade replies sent by other users when sending those replies on to you.
+
+The tag MUST be named ``solanum.chat/reply`` and specifies no value.
+
+Example
+-------
+
+Consider the example of a user ``fred`` replying to user ``bob`` in a channel you're in, once you've requested this capability
+
+::
+
+    @msgid=QgAABclB :bob PRIVMSG #solanum :nice weather today!
+    @+reply=QgAABclB;msgid=wfMKLH5M :fred PRIVMSG #solanum :for ducks!
+
+and consider the example of the same, but you have not requested this capability
+
+::
+
+    :bob PRIVMSG #solanum :nice weather today!
+    :fed PRIVMSG #solanum :bob: for ducks!