Update SdkConfig usage to use new translation layer + update config.md docs (#21429)

* Update SdkConfig usage to use new translation layer

* Appease the linter

* WIP refactor of config documentation

* Finish re-writing config.md

* Update surrounding documentation

* Apply suggestions from code review

Co-authored-by: Germain <germains@element.io>

* Textual updates

Co-authored-by: Germain <germains@element.io>

src/async-components/structures/CompatibilityView.tsx

@@ -27,7 +27,8 @@ interface IProps {
 }
 
 const CompatibilityView: React.FC<IProps> = ({ onAccept }) => {
-    const { brand, mobileBuilds } = SdkConfig.get();
+    const brand = SdkConfig.get("brand");
+    const mobileBuilds = SdkConfig.get("mobile_builds");
 
     let ios = null;
     const iosCustomUrl = mobileBuilds?.ios;