Basic modal for switching extension settings (#907)

* Basic modal for switching extension settings

* Improve network usage by including field in query directly

Requesting individually is stupid, when it's a field that is already
available on the server

* Improve extension slider usability

- Always render the element, fixes animations
- Store the selected item in state, allows the back-button to re-open
  dialog

* Update src/modules/extension/components/ExtensionOptions.tsx

Co-authored-by: schroda <50052685+schroda@users.noreply.github.com>

* Update src/modules/extension/components/ExtensionOptions.tsx

Co-authored-by: schroda <50052685+schroda@users.noreply.github.com>

* Fix suggestions

* Use dialog instead of optionsPanel

* Extension options remove redundant NSFW info

* Apply suggestions from code review

Co-authored-by: schroda <50052685+schroda@users.noreply.github.com>

* Use proper dialog title and content for settings dialog

* Use `string | undefined` instead of `string | null` to satisfy `tsc`

---------

Co-authored-by: schroda <50052685+schroda@users.noreply.github.com>

public/locales/en.json

@@ -292,6 +292,9 @@
             "title": "Extension repositories"
           }
         }
+      },
+      "dialog": {
+        "title": "Per-language extension settings"
       }
     },
     "state": {