Improved Nested Docs and Link Grouping Support (#147)

* added a table of content

* wide layout for docs, styles for the table of content

* fixes for docs layout

* wide footer at the docs section

* added support for nested docs, added toggling groups of links, delimiters, external links

* external link icon

* added active state for nested links, styles for the external link icon

* styles fix

* remove doc sync

* update directory structure and doc titles

* fix outstanding links

* fix more links for merge

* Revert "fix more links for merge"

This reverts commit 46c9ccaf1b7765f2cda8dc85d625fa6b4e3f5436.

* Revert "fix outstanding links"

This reverts commit 28e6380b74f1ab74690c8184551f186656d6d4e9.

* fix remaining broken links

* move how-to tutorials in the different page

* split tutorials

* fix link

* upd github edit link

* skip empty index pages

---------

Co-authored-by: Andrey Vasnetsov <andrey@vasnetsov.com>
Co-authored-by: David Sertic <62056091+davidmyriel@users.noreply.github.com>

qdrant-landing/themes/qdrant/layouts/partials/table_of_content.html

@@ -0,0 +1,15 @@
+{{$currentNode := .}}
+<nav class="tableOfContent col-lg-2 col-12 d-lg-block d-none mt-0 pr-4 mb-4">
+
+    {{ $sectionLink := cond .IsSection .RelPermalink .Parent.RelPermalink }}
+    {{ $subject := site.GetPage $sectionLink }}
+    <div class="sticky-top">
+        {{ range $subject.RegularPages }}
+            {{ if eq .File.UniqueID $currentNode.File.UniqueID }}
+                <h5 class="tableOfContent__header">Table of contents</h5>
+                {{ .TableOfContents }}
+            {{ end }}
+        {{ end }}
+        <br/>
+    </div>
+</nav>