Refactor page meta (#2641)

* Rename include

* Add grid view test pages

* Rename `.post__meta-sep` and use CSS to add line break

* Improve collection grid archive

* Improve page grid archive

* Enable `grid`

* Don't show date icon if there is no `date` value

* Add blank line at EOF

* Add space

* Wrap date and reading time in named `span` elements