[mod] replace /help by /info pages and include pages in project docs

This patch implements a bolierplate to share content from info-pages of the
SearXNG instance (URL /info) with the project documentation (path /docs/user).

The info pages are using Markdown (CommonMark), to include them in the project
documentation (reST) the myst-parser [1] is used in the Sphinx-doc build chain.

If base_url is known (defined in settings.yml) links to the instance are also
inserted into the project documentation::

    searxng_extra/docs_prebuild

[1] https://www.sphinx-doc.org/en/master/usage/markdown.html

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/templates/simple/base.html

@@ -58,7 +58,7 @@
   </main>
   <footer>
     <p>
-    {{ _('Powered by') }} <a href="{{ url_for('help_page', pagename='about') }}">searxng</a> - {{ searx_version }} — {{ _('a privacy-respecting, hackable metasearch engine') }}<br/>
+    {{ _('Powered by') }} <a href="{{ url_for('info', pagename='about', locale=current_locale) }}">searxng</a> - {{ searx_version }} — {{ _('a privacy-respecting, hackable metasearch engine') }}<br/>
         <a href="{{ searx_git_url }}">{{ _('Source code') }}</a> |
         <a href="{{ get_setting('brand.issue_url') }}">{{ _('Issue tracker') }}</a> |
         <a href="{{ url_for('stats') }}">{{ _('Engine stats') }}</a> |

searx/templates/simple/help.html

@@ -1,12 +0,0 @@
-{% extends 'simple/page_with_header.html' %}
-{% block title %}{{ page.title }} - {% endblock %}
-{% block content %}
-<ul class="tabs">
-{% for name, page in all_pages %}
-  <li>
-    <a href="{{name}}" {% if name == page_filename %}class="active"{% endif %}>{{page.title}}</a>
-  </li>
-{% endfor %}
-</ul>
-{{ page.content | safe }}
-{% endblock %}

searx/templates/simple/info.html

@@ -0,0 +1,14 @@
+{% extends 'simple/page_with_header.html' %}
+{% block title %}{{ active_page.title }} - {% endblock %}
+{% block content %}
+<ul class="tabs">
+{% for pagename, page in all_pages('en') %}
+  <li>
+    <a href="{{pagename}}" {% if pagename == active_pagename %}class="active"{% endif %}>{{page.title}}</a>
+  </li>
+{% endfor %}
+</ul>
+<div class="info-page {{pagename}}">
+  {{- active_page.html | safe -}}
+</div>
+{% endblock %}