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
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}