help-beta: Merge lists of same type adjacent to each other.

Fixes #31252.
One of our major use cases for file imports is to have bullet points as
partials to import at different places in the project. But when
importing the file with Astro, it creates its own lists. So we merge
lists together if they have nothing but whitespace between them.
There were some talks to use a component called FlattenList that would
flatten the list inside it, but that would also flatten lists that were
nested on purpose. This approach while feeling a bit hacky would not
flatten nested lists.

tools/convert-help-center-docs-to-mdx

@@ -176,6 +176,10 @@ def run() -> None:
     include_source_dir = os.path.join(BASE_DIR, "help/include")
     include_destination_dir = os.path.join(BASE_DIR, "help-beta/src/content/docs/include")
     shutil.copytree(include_source_dir, include_destination_dir)
+
+    # We do not want Astro to render these include files as standalone
+    # files, prefixing them with an underscore accomplishes that.
+    # https://docs.astro.build/en/guides/routing/#excluding-pages
     for name in os.listdir(include_destination_dir):
         os.rename(
             os.path.join(include_destination_dir, name),