templater: move stylemap() to hgweb_mod, since that's its only user
`stylemap()` even has an error message that mentions "hgweb
templates", so it seems that it's meant specifically for hgweb.
Differential Revision: https://phab.mercurial-scm.org/D8890
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true