re documentation issue

[heikkitoivonen]

• docs/stdlib/re.md understates re.compile(). It only mentions the O(n²) shared-prefix case. Because re.compile uses the same parser, it also pays:
  • O(n²) for a long run of (?:..) groups;
  • O(n·d) for groups nested d deep;
  • a cost for the code points a character-class range covers.