Update README

Signed-off-by: Janne Savolainen <janne.savolainen@live.fi>

packages/technical-features/application/electron-main/README.md

@@ -1,3 +1,35 @@
 # @k8slens/application-for-electron-main
 
-TBD
+This Feature extends `@k8slens/application` with Electron specifics.
+
+# Usage
+```bash
+$ npm install @k8slens/application-for-electron-main
+```
+
+```typescript
+import { applicationFeature, startApplicationInjectionToken } from "@k8slens/application";
+import { applicationFeatureForElectronMain } from "@k8slens/application-for-electron-main";
+import { registerFeature } from "@k8slens/feature-core";
+import { createContainer } from "@ogre-tools/injectable";
+
+const di = createContainer("some-container");
+
+registerFeature(di, applicationFeature, applicationFeatureForElectronMain);
+
+const startApplication = di.inject(startApplicationInjectionToken);
+
+startApplication();
+```
+
+# Extendability
+
+### Timeslots
+
+#### `beforeAnythingInjectionToken`
+
+Runnables registered here will be called before anything else. **Special requirement** here is that everything here needs to be synchronous.
+
+#### `beforeElectronIsReadyInjectionToken`
+
+Runnables registered here will be called right after runnables in `beforeAnythingInjectionToken` but still before we are sure that Electron application is ready (`electron.app.whenReady()`). **Special requirement** here is that everything here needs to be synchronous.