add suppport for listing preferred and default projects

fix #3 (closed)

add preferred projects, which are chosen over "normal" project in case of tie, and default_project, so that #12345 can match some predefined project.
This configuration is per channel. I've put tpo/core/team as a default for #tor-dev, but it's just a showcase, this repo is hardly ever referenced in practice

config/main.yaml

@@ -16,6 +16,10 @@ irc:
     tls_auth_key: ~/bot/tls-auth.key
   channels:
     - channel: "#tor-dev"
+      default_project: "tpo/core/team"
+      preferred_projects:
+        - "tpo/core/tor"
+        - "tpo/anti-censorship/pluggable-transports/snowflake"
     - channel: "#tor-project"
     - channel: "#tor-bot-test"