Add warnings flag

This commit adds a warnings flag

It can be combined with -q / --quiet to display warnings.
The intent is to provide a silent option that still surfaces
warning and error messages so that they are visible in logs.

gallery_dl/__init__.py

@@ -113,7 +113,7 @@ def main():
 
         # loglevels
         output.configure_logging(args.loglevel)
-        if args.loglevel >= logging.ERROR:
+        if args.loglevel >= logging.WARNING:
             config.set(("output",), "mode", "null")
             config.set(("downloader",), "progress", None)
         elif args.loglevel <= logging.DEBUG:

gallery_dl/option.py

@@ -255,6 +255,12 @@ def build_parser():
         action="store_const", const=logging.DEBUG,
         help="Print various debugging information",
     )
+    output.add_argument(
+        "-w", "--warning",
+        dest="loglevel",
+        action="store_const", const=logging.WARNING,
+        help="Print warnings",
+    )
     output.add_argument(
         "-g", "--get-urls",
         dest="list_urls", action="count",