Fix #178: Foundations for API documentation with Swagger

changes/changelog.d/178.doc

+Foundations for API documentation with Swagger (#178)

docs/api.rst

+Funkwhale API
+=============
+
+Funkwhale API is still a work in progress and should not be considered as
+stable. We offer an `interactive documentation using swagger </swagger/>`_
+were you can browse available endpoints and try the API.

docs/index.rst

@@ -16,6 +16,7 @@ Funkwhale is a self-hosted, modern free and open-source music server, heavily in
    configuration
    importing-music
    federation
+   api
    upgrading
    changelog