Alter behaviour of --skip-dl to allow DRM licensing

Most people used --skip-dl just to license the DRM pre-v1.3.0. Which makes sense, --skip-dl is otherwise a pointless feature. I've fixed it so that --skip-dl worked like before, allowing license calls, while still supporting the new per-segment features post-v1.3.0.

Fixes #37

devine/core/manifests/hls.py

@@ -184,6 +184,7 @@ class HLS:
         save_path: Path,
         save_dir: Path,
         stop_event: Event,
+        skip_event: Event,
         progress: partial,
         session: Optional[Session] = None,
         proxy: Optional[str] = None,
@@ -280,6 +281,10 @@ class HLS:
                 finally:
                     segment_key.put(newest_segment_key)
 
+                if skip_event.is_set():
+                    progress(downloaded="[yellow]SKIPPING")
+                    return 0
+
             if not segment.uri.startswith(segment.base_uri):
                 segment.uri = segment.base_uri + segment.uri