tools: Add tool to count contributions across all major repositories.
tools: Add tool to count contributions across all major repositories.

This will allow Zulip release announcements to credit contributions
made to Zulip projects beyond the server in our release announcements.

Fixes #19044.

kou/zulip,kou/zulip,andersk/zulip,rht/zulip,zulip/zulip,rht/zulip,rht/zulip,kou/zulip,kou/zulip,zulip/zulip,andersk/zulip,zulip/zulip,rht/zulip,andersk/zulip,zulip/zulip,zulip/zulip,andersk/zulip,rht/zulip,andersk/zulip,kou/zulip,andersk/zulip,rht/zulip,zulip/zulip,rht/zulip,kou/zulip,andersk/zulip,kou/zulip,zulip/zulip