Revert "Remove Python 3.6 support"

This reverts commit 6929b41a21.

yt_dlp/compat/re.py

@@ -0,0 +1,18 @@
+# flake8: noqa: F405
+from re import *  # F403
+
+from .compat_utils import passthrough_module
+
+passthrough_module(__name__, 're')
+del passthrough_module
+
+try:
+    Pattern  # >= 3.7
+except NameError:
+    Pattern = type(compile(''))
+
+
+try:
+    Match  # >= 3.7
+except NameError:
+    Match = type(compile('').match(''))