docs: set instead of list for allowed_file_exts

Author: NickVeld

README.md

@@ -627,7 +627,7 @@ Ways to change the global configurations are below -
 
     # list of allowed file extensions
     # shortend for readability
-    'ALLOWED_FILE_EXT': ['.html', '.css', ...]
+    'ALLOWED_FILE_EXT': {'.html', '.css', ...}
 
     # log file path
     'LOG_FILE': None

docs/configurations.md

@@ -87,7 +87,7 @@ below is the list of `config` keys with their `default` values :
 
     # list of allowed file extensions
     # shortend for readability
-    'ALLOWED_FILE_EXT': ['.html', '.css', ...]
+    'ALLOWED_FILE_EXT': {'.html', '.css', ...}
 
     # log file path
     'LOG_FILE': None