docs: adding mentions of this site's source available (closing #2)

docs/index.md

@@ -12,3 +12,9 @@ We have many things. Yes.
 - :simple-forgejo: [git.jakest.us](http://git.jakest.us)
 - :simple-matrix: [@jt:neo.jakest.us](https://matrix.to/#/@jt:neo.jakest.us)
 - :simple-mastodon: [@jt@bubbler.jakest.us](http://bubbler.jakest.us/@jt)
+
+Source code of this web site is available at
+[:simple-git: my git](https://git.jakest.us/jt/saitti) .
+If you find an error, please feel free to contact me at my socials
+or drop a PR (if I ever open registration or you are one of the
+special people...)

mkdocs.yml

@@ -26,6 +26,9 @@ extra:
     - icon: simple/forgejo
       link: https://git.jakest.us
       name: My codings on git
+    - icon: simple/git
+      link: https://git.jakest.us/jt/saitti
+      name: Website source code
 extra_css:
   - extra.css
 markdown_extensions: