Update book defaults and add link to GH

Author: rustprooflabs

docs/book.toml

@@ -4,3 +4,9 @@ language = "en"
 multilingual = false
 src = "src"
 title = "PgOSM Flex Faker"
+
+[output.html]
+default-theme = "rust"
+preferred-dark-theme = "navy"
+git-repository-url = "https://github.com/rustprooflabs/pgosm-flex-faker"
+git-repository-icon = "fa-github"