init: add daemon.lock to .gitignore (#156)

The daemon.lock file should be ignored in git since it's a runtime
file created by the daemon to manage exclusive database access.

Amp-Thread-ID: https://ampcode.com/threads/T-b77cef77-966d-4917-b605-4d2b2fb546e1

Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/init.go

@@ -90,6 +90,7 @@ and database file. Optionally specify a custom issue prefix.`,
 *.db-shm
 
 # Daemon runtime files
+daemon.lock
 daemon.log
 daemon.pid
 bd.sock