[Enhancement] Add navigation to previous / next documents

[Ibochkarev]

For ease of use, add navigation through the previous and next documents from the currently viewed document.
Locate at the very bottom of the page.

Example:

[wax100]

I think we can use Minishop2 as example

I also use pdoNeighbors with a slight variation along with Bootstrap classnames in my latest incarnation of my own site.

[[pdoNeighbors? 
   &tplWrapper=`@INLINE <div class="d-flex justify-content-center my-4">[[+prev]][[+up]][[+next]]</div>`
   &tplPrev=`@INLINE <span class="btn btn-outline-primary mx-2"><a href="/[[+uri]]">&larr; [[+menutitle]]</a></span>`
   &tplNext=`@INLINE <span class="btn btn-outline-primary mx-2"><a href="/[[+uri]]">[[+menutitle]] &rarr;</a></span>`
   &tplUp=`@INLINE <span class="btn btn-outline-primary">&uarr; <a href="/[[+uri]]">[[+menutitle]]</a></span>`
   &showHidden=`0

[wax100]

Will try to add ...

[Mark-H]

Just to clarify for people coming across this in the future, this issue is for adding prev/next to the documentation site - not to MODX itself.