Fix SyntaxWarnings due to invalid escape sequences (Python 3.12 compatibility)

[Arian-Ott]

Hi,
I'm the Debian maintainer for python-jieba.
While testing with recent Python versions, we noticed several
SyntaxWarning: invalid escape sequence warnings.

I've attached a patch that fixes these by using raw strings for regex. We are already using this fix in Debian.

0002-fix-syntax-warnings.patch

Best regards,
Arian Ott