[enh] make searx.user_help use an explicit TOC

When we have multiple help pages we want them
to be displayed in a specific order.

searx/user_help.py

@@ -1,6 +1,5 @@
 # pyright: basic
 from typing import Dict, NamedTuple
-import os.path
 import pkg_resources
 
 import flask
@@ -16,6 +15,9 @@ class HelpPage(NamedTuple):
     content: str
 
 
+# Whenever a new .md file is added to help/ it needs to be added here
+_TOC = ('about',)
+
 PAGES: Dict[str, HelpPage] = {}
 """ Maps a filename under help/ without the file extension to the rendered page. """
 
@@ -44,21 +46,16 @@ def render(app: flask.Flask):
 
     define_link_targets = ''.join(f'[{name}]: {url}\n' for name, url in link_targets.items())
 
-    for filename in pkg_resources.resource_listdir(__name__, 'help'):
-        rootname, ext = os.path.splitext(filename)
-
-        if ext != '.md':
-            continue
-
-        file_content = pkg_resources.resource_string(__name__, 'help/' + filename).decode()
+    for pagename in _TOC:
+        file_content = pkg_resources.resource_string(__name__, 'help/' + pagename + '.md').decode()
         markdown = define_link_targets + file_content
         assert file_content.startswith('# ')
         title = file_content.split('\n', maxsplit=1)[0].strip('# ')
         content: str = mistletoe.markdown(markdown)
 
-        if filename == 'about.md':
+        if pagename == 'about':
             try:
                 content += pkg_resources.resource_string(__name__, 'templates/__common__/aboutextend.html').decode()
             except FileNotFoundError:
                 pass
-        PAGES[rootname] = HelpPage(title=title, content=content)
+        PAGES[pagename] = HelpPage(title=title, content=content)