typing: add stub functions for `cext/charencoding`
I'm not sure if it's better to have a separate file, and currently pytype
doesn't really know how to handle these, so it's no help in figuring that out.
Technically, these methods are part of the `mercurial.cext.parsers` module, so
put them into the existing stub until there's a reason to split it out.
[build-system]
requires = ["setuptools", "wheel"]
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true