Add server status page and a badge in AppBar (#182)

* WIP: Add server status and running process indicators

* Finish ServerStatusPage and ServerRunningProcess

* fix typos, add running process info to the server status page

* Remove ServerRunningProcess and integrate it into ServerStatusBadge

* remove divider in menu

* display time as started X minutes ago

* add documentation; clearly state what new components are; update readme

* change wording a bit, cross-link with docs/README.md

* use returned HTML

* Finish ServerStatus page and badges

* Fix types

* cleanup

* remove some code

* adjust config load

docs/README.md

@@ -26,6 +26,14 @@ Specific configuration options:
 * [User Badges](./user-badges.md)
 * [Prefilling the Login Form](./prefill-login-form.md)
 
+for [etke.cc](https://etke.cc) customers only:
+
+> **Note:** The following features are only available for etke.cc customers. Due to specifics of the implementation,
+they are not available for any other Synapse Admin deployments.
+
+* [Server Status icon](../src/components/etke.cc/README.md#server-status-icon)
+* [Server Status page](../src/components/etke.cc/README.md#server-status-page)
+
 ## Deployment
 
 * [Serving Synapse Admin behind a reverse proxy](./reverse-proxy.md)