fix(docs): remove trailing slash from html5 void elements

[Rotzbua]

Fix #537

[4levels]

Allthough I agee with the comment on the related issue, that this is merely a preference change, for consistency reasons I'd agree with this PR. If you look at the diff in the readme file and see eg. how <meta tags are currently used both with and without the end /> tag I'd prefer consistency to win the argument here ;-)

[lucaslarroche]

Thanks @Rotzbua for this, and sorry for the delay!
I’m all for consistency, so I really appreciate you spotting this. I’ll merge the PR into dev now, and it will be shipped with the next release.