feat: add (incomplete) nix flake

dave.py isn't packaged yet. Will try to do this myself but dealing with
vcpkg is a bit annoying.

errornocord/fun.py

@@ -0,0 +1,13 @@
+import random
+
+from . import commands
+from .constants import REACTIONS
+
+
+async def on_message(message):
+    if random.random() < 0.01:
+        tokens = commands.tokenize(message.content, remove_prefix=False)
+        for keyword, options in REACTIONS.items():
+            if keyword in tokens:
+                await message.add_reaction(random.choice(options))
+                break