[feat] allow customization of logo and favicon

also removed searxng-wordmark from templates directory and build
files, because it is no longer used anywhere

searx/settings.yml

@@ -29,6 +29,12 @@ brand:
   #   links:
   #     Uptime: https://uptime.searxng.org/history/darmarit-org
   #     About: "https://searxng.org"
+  # custom_files:
+  #   # If using custom logo, be sure to set the right file extension as it's used to determine the mimetype.
+  #   logo: /path/to/file.png
+  #   # For custom favicons, you must include a PNG version, as some browsers still don't support SVG favicons.
+  #   favicon_png: /path/to/file.png
+  #   favicon_svg: /path/to/file.svg
 
 search:
   # Filter results. 0: None, 1: Moderate, 2: Strict