docs: ✏️ update decomentation

Author: mjancarik

website/docs/error-plugin.md

@@ -98,3 +98,24 @@ When an error is thrown, the plugin does the following:
   ```
 * [emit](/docs/event-emitter-plugin#emit) `ERROR` event with thrown error
 * Re-runs the function (if defined)
+
+The error object is available everywhere in the widget, as well as to the host application.
+
+## Limitations
+
+The plugin can't handle errors occurring outside of lifecycle functions.
+
+## Custom errors
+
+You can throw custom errors by instantiating `GenericError` class or create custom error classes that extend `GenericError`.
+
+`GenericError` class carries `status` param among with other params. This way error plugin can respond with adequate HTTP status and also include data for encountered error.
+
+```javascript
+import { GenericError } from '@merkur/plugin-error';
+
+throw new GenericError('Operation failed.', {
+  status: 500,
+  reason: 'api_error'
+})
+```

website/docs/integration-with-app.md

@@ -347,3 +347,30 @@ return (
   </MerkurSlot>
 )
 ```
+
+## Merkur Dev Client
+When integrating Merkur widgets into an existing application, developers often face challenges with the development workflow - particularly with hot module replacement (HMR). The Merkur Dev Client solves this problem by bringing the same seamless development experience you get in the playground directly to your integrated application.
+### Bringing Playground Experience to Your Application
+The Merkur Dev Client enables the same fluid development experience you enjoy in the playground environment when working with your widget in any integrated application:
+- **Real-time Widget Updates**: Edit your widget code and see changes instantly in your application
+- **No Application Refreshes**: Updates are applied without reloading the entire application
+- **Preserve Application State**: Keep authentication, form inputs, and application context intact during development
+### Enabling the Dev Client
+To enable the Dev Client in your host application, simply add the following script tag to your HTML head:
+```html
+<script src="http://localhost:4445/__dev__/js/merkurDevClient.js"></script>
+```
+For server-side templates (like EJS), you can conditionally include it only in development mode:
+```ejs
+<% if (process.env.NODE_ENV === 'development') { %>
+  <script src="http://localhost:4445/__dev__/js/merkurDevClient.js"></script>
+<% } %>
+```
+### How Dev Client Works
+The Dev Client works by:
+1. Establishing a WebSocket connection to your Merkur dev server
+2. Monitoring changes to Merkur widget assets (scripts, styles)
+3. Automatically replacing or updating affected assets when changes are detected
+4. Hooking into the Merkur widget creation process to track active widgets within your application
+Assets are tracked using the `data-merkur-asset-name` attribute, which the Dev Client uses to identify and update them without reloading the entire application page.
+The Dev Client is automatically configured when running your widget in development mode with the Merkur CLI (`merkur dev`), and only requires adding a single script tag to your host application.

website/docs/merkur-cli.md

@@ -10,7 +10,7 @@ Merkur CLI for building your widget use [esbuild](https://esbuild.github.io/) to
 
 ## Commands
 
-- `merkur dev` - build your widget with with NODE_ENV = 'development' and with watch mode
+- `merkur dev` - build your widget with NODE_ENV = 'development' and with watch mode. Enables [Merkur Dev Client](/docs/integration-with-app#merkur-dev-client) for hot module replacement
 - `merkur build` - build your widget with NODE_ENV = 'production'
 - `merkur test` - run defined widget tests with NODE_ENV = 'test'
 - `merkur start` - run widget server and playground server

website/docs/storybook-integration-into-merkur.md

@@ -122,4 +122,3 @@ TenCounter.args = {
 ```
 
 Now run command `npm run storybook` and you will see our Counter component with two settings.
-```