[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>

docs/conf.py

@@ -35,7 +35,7 @@ master_doc = "index"
 source_suffix = '.rst'
 numfig = True
 
-exclude_patterns = ['build-templates/*.rst']
+exclude_patterns = ['build-templates/*.rst', 'user/*.md']
 
 import searx.engines
 import searx.plugins
@@ -94,7 +94,6 @@ extlinks['pull-searx'] = ('https://github.com/searx/searx/pull/%s', 'PR ')
 # links to custom brand
 extlinks['origin'] = (GIT_URL + '/blob/' + GIT_BRANCH + '/%s', 'git://')
 extlinks['patch'] = (GIT_URL + '/commit/%s', '#')
-extlinks['search'] = (SEARXNG_URL + '/%s', '#')
 extlinks['docs'] = (DOCS_URL + '/%s', 'docs: ')
 extlinks['pypi'] = ('https://pypi.org/project/%s', 'PyPi: ')
 extlinks['man'] = ('https://manpages.debian.org/jump?q=%s', '')
@@ -123,8 +122,11 @@ extensions = [
     'linuxdoc.rstFlatTable',    # Implementation of the 'flat-table' reST-directive.
     'linuxdoc.kfigure',         # Sphinx extension which implements scalable image handling.
     "sphinx_tabs.tabs", # https://github.com/djungelorm/sphinx-tabs
+    'myst_parser',  # https://www.sphinx-doc.org/en/master/usage/markdown.html
 ]
 
+suppress_warnings = ['myst.domains']
+
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3/", None),
     "flask": ("https://flask.palletsprojects.com/", None),