[Bug web/87050] Bump wwwdocs to html5

[jb at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87050

--- Comment #4 from Janne Blomqvist <jb at gcc dot gnu.org> ---
Sure, I can chip in a little, though I'm no html expert. Do you have some
branch somewhere where you're working, or?