Doc: Set favicon (#820)

mkdocs.yml

@@ -5,6 +5,7 @@ theme:
   icon:
     repo: fontawesome/brands/github
   logo: assets/swe-agent.svg
+  favicon: assets/swe-agent.svg
   palette:
     - media: "(prefers-color-scheme)"
       toggle:
@@ -100,4 +101,4 @@ repo_url: https://github.com/princeton-nlp/SWE-agent
 repo_name: princeton-nlp/SWE-agent
 edit_uri: edit/main/docs/
 extra_css:
-  - assets/custom.css
+  - assets/custom.css