DeprecationWarning: 'cgi' is deprecated and slated for removal in Python 3.13

[Vinfall]

I got the warning DeprecationWarning: 'cgi' is deprecated and slated for removal in Python 3.13 after Void Linux bumped the default Python version from 3.10 to 3.11 (yet I don't know why Termux with Python 3.11 does not show the warning, maybe because I installed it from PyPI?).

Although it could take a lot of time for us to get our hands on 3.13, it's still better to get prepared in advance.

There are two ways:

1. Suppress the warning like DeprecationWarning: 'cgi' is deprecated and slated for removal in Python 3.13 beeware/briefcase#868, but I don't see buku use pyproject.toml
2. Replace cgi.parse_header with email.message as was mentioned in DeprecationWarning: 'cgi' is deprecated and slated for removal in Python 3.13 Pylons/webob#437 and https://peps.python.org/pep-0594/#cgi.

I took a brief look at the ToDo list, coding guideline and code base, it seems that cgi is rarely used so the fix should be simple.

Just these lines?

buku/buku

Lines 3809 to 3820 in 4384cbd

	if soup.meta and soup.meta.get('charset') is not None:
	charset = soup.meta.get('charset')
	elif 'content-type' in resp.headers:
	_, params = cgi.parse_header(resp.headers['content-type'])
	if params.get('charset') is not None:
	charset = params.get('charset')
	if not charset and soup:
	meta_tag = soup.find('meta', attrs={'http-equiv': 'Content-Type'})
	if meta_tag:
	_, params = cgi.parse_header(meta_tag.attrs['content'])
	charset = params.get('charset', charset)

A sample fix: https://github.com/Vinfall/buku/commit/5de3c11e559c5700f62c8961460ce0497e3275fe.

If you'd liike to remove the warning for now, I can raise a PR 😆.

[jarun]

Please raise the PR.