[Docs] Create summary page for directives

[andsel]

Is your feature request related to a problem? Please describe.
Create a page in the documentation to summary all the tags available

Describe the solution you'd like
Create a new documentation page to be added in the leftside list (docs/modules/ROOT/nav.adoc) .
This page should list all available tags, a short description for the intended use and a set of links to the other pages where they are describe in more depth.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Raised as a request in #2013 (comment)

[maxandersen]

Good idea.

Btw i can see we aren't consistent on what we call these in our docs.

The proper word is directives not tags.

[quintesse]

Sorry, I always say "tags", that name probably just got stuck in my head years ago :-)
I'll try to use "directives" from now on!