Update layzload and (local/roxy) Rescr logic.

Set lazyload and resrc independently from each other in config, update how to description, both in config and head scripts.
Update html_head snippet include.

Set criticalcss var to fals except for the home template; remove the prerender var.
Fix lang attribute, multi languages support and sitemap.

Udpate to new multi language config settings; add `/site/languages/` folder with UI translation placeholder files, update sitemap generation with correct mult language support, fix language toggle snippet, update logic of alternate lang rel links, etc.
Minor tweaks of head snippets.

Simplify robot meta tag logic, change order, and update/fix canonical rel link.
Fix pagination limit for Kirby 2.
Set default video width and height in config.

Config vartiable was already present, but was not used in video snippet.
Extra line.