Resolves #10923

Rebased from #10930
add explicit copyright header to docs CSS & JS files; fixes #11112
even shorter banner; remove space between slash and period
Merge branch 'fix-11112'
copy change, add to buttons anchor section
Merge branch 'master' into navbar-button-docs
Merge pull request #11096 from twbs/navbar-button-docs

Resolves #10923