Third proposal, meta tags in html, draft for review

Dear participants, 

I also prepared the third draft we talked about, i.e. about the use of meta tags in (x)html content. This way we may go quicker to some choices (or hybridation). 

https://github.com/w3c/tdm-reservation-protocol/blob/main/proposals/proposal-html-meta.md <https://github.com/w3c/tdm-reservation-protocol/blob/main/proposals/proposal-html-meta.md>

Robots meta directives have been used as a source of ideas here also. 

Best regards
Laurent