Enhance verbosity with detailed download progress information (#28)

This PR uses yt_dlp's progress_hooks to log information about percentage
completed (`d['_percent_str']`) and download speed (`d['_speed_str']`).
This addition aims to provide more insights into the ongoing download
process, assisting users or developers in monitoring and understanding
the progress of the operation.

xklb/tube_backend.py

@@ -349,6 +349,9 @@ def out_dir(p):
         },
     }
 
+    if args.verbose >= consts.LOG_DEBUG:
+        func_opts["progress_hooks"] = [lambda d: log.debug(f"downloading {d['_percent_str']} {d['_speed_str']}")]
+
     if args.profile != DBType.audio:
         func_opts["subtitlesformat"] = "srt/best"
         func_opts["subtitleslangs"] = args.subtitle_languages