Plugins: Fix python 3.14 compatibility

This commit ensures global flags to be located at very first character
of patterns, as it is what python 3.14 enforces.

Author: deathaxe

plugins/headings/level.py

@@ -78,8 +78,7 @@ def _set_level(self, edit, calc_level, select):
         view = self.view
         match_heading_hashes = view.settings().get("mde.match_heading_hashes")
         pattern = re.compile(
-            r"""
-            (?x)
+            r"""(?x)
             ^([ \t>]*)                   # block quotes
             (?:
                 (\#+)                    # leading hashes