[options] add '--config-json' command-line option

docs/options.md

@@ -138,7 +138,9 @@
 
 ## Configuration Options:
     -o, --option KEY=VALUE      Additional options. Example: -o browser=firefox
-    -c, --config FILE           Additional configuration files in JSON format
+    -c, --config FILE           Additional configuration files in default
+                                format
+    --config-json FILE          Additional configuration files in JSON format
     --config-yaml FILE          Additional configuration files in YAML format
     --config-toml FILE          Additional configuration files in TOML format
     --config-type TYPE          Set filetype of default configuration files

gallery_dl/__init__.py

@@ -33,8 +33,10 @@ def main():
                 config.log.error(exc)
         if args.config_load:
             config.load()
+        if args.configs_extra:
+            config.load(args.configs_extra, strict=True)
         if args.configs_json:
-            config.load(args.configs_json, strict=True)
+            config.load(args.configs_json, strict=True, loads=util.json_loads)
         if args.configs_yaml:
             import yaml
             config.load(args.configs_yaml, strict=True, loads=yaml.safe_load)

gallery_dl/option.py

@@ -616,6 +616,11 @@ def build_parser():
     )
     configuration.add_argument(
         "-c", "--config",
+        dest="configs_extra", metavar="FILE", action="append",
+        help="Additional configuration files in default format",
+    )
+    configuration.add_argument(
+        "--config-json",
         dest="configs_json", metavar="FILE", action="append",
         help="Additional configuration files in JSON format",
     )