Consolidate all demos under demo/ + add rosocket demo (#1503)

- Move `electron_demo/` → `demo/electron/` and `ts_demo/` → `demo/typescript/`, so all runnable demos live under a single `demo/` tree (Electron, TypeScript, and the new rosocket demo). Path-only renames; per-demo READMEs and the top-level `README.md`, `scripts/npmjs-readme.md`, `eslint.config.mjs`, and `.npmignore` are updated to reference the new locations.
- Add `demo/rosocket/` — a minimal end-to-end example of the `rosocket` WebSocket bridge: a Node `server.js` that wires `/chatter` (`std_msgs/msg/String`) and `/add_two_ints` (`example_interfaces/srv/AddTwoInts`) to plain WebSocket URLs, and a single-file `index.html` browser client (no client library, just built-in `WebSocket` + `JSON`) demonstrating subscribe / publish / service-call. README documents how to source ROS 2, run the bridge alongside the existing AddTwoInts service example, open the page from any modern browser, and verify the round-trip from the ROS 2 side.

Fix: #1502

Author: minggangw

.npmignore

@@ -26,6 +26,7 @@ tutorials/
 electron_demo/
 ts_demo/
 tools/
+demo/
 .github/
 .nyc_output/
 .vscode/

README.md

@@ -144,10 +144,10 @@ Create rich, interactive desktop applications using Electron and web technologie
 
 |                       Demo                        |                                                              Description                                                              |                            Screenshot                            |
 | :-----------------------------------------------: | :-----------------------------------------------------------------------------------------------------------------------------------: | :--------------------------------------------------------------: |
-|  **🐢 [turtle_tf2](./electron_demo/turtle_tf2)**  |  Real-time coordinate frame visualization with turtle control. Features TF2 transforms, keyboard control, and dynamic frame updates.  |  ![turtle_tf2](./electron_demo/turtle_tf2/turtle-tf2-demo.png)   |
-| **🦾 [manipulator](./electron_demo/manipulator)** | Interactive two-joint robotic arm simulation. Features 3D joint visualization, manual/automatic control, and visual movement markers. | ![manipulator](./electron_demo/manipulator/manipulator-demo.png) |
+|  **🐢 [turtle_tf2](./demo/electron/turtle_tf2)**  |  Real-time coordinate frame visualization with turtle control. Features TF2 transforms, keyboard control, and dynamic frame updates.  |  ![turtle_tf2](./demo/electron/turtle_tf2/turtle-tf2-demo.png)   |
+| **🦾 [manipulator](./demo/electron/manipulator)** | Interactive two-joint robotic arm simulation. Features 3D joint visualization, manual/automatic control, and visual movement markers. | ![manipulator](./demo/electron/manipulator/manipulator-demo.png) |
 
-Explore more examples in [electron_demo](https://github.com/RobotWebTools/rclnodejs/tree/develop/electron_demo).
+Explore more examples in [demo/electron](https://github.com/RobotWebTools/rclnodejs/tree/develop/demo/electron).
 
 ## Using rclnodejs with TypeScript
 
@@ -175,7 +175,7 @@ rclnodejs.init().then(() => {
 });
 ```
 
-See [TypeScript demos](https://github.com/RobotWebTools/rclnodejs/tree/develop/ts_demo) for more examples.
+See [TypeScript demos](https://github.com/RobotWebTools/rclnodejs/tree/develop/demo/typescript) for more examples.
 
 ## Observable Subscriptions
 

electron_demo/README.md demo/electron/README.mdelectron_demo/README.md renamed to demo/electron/README.md

@@ -25,7 +25,7 @@ An interactive Electron application demonstrating a two-joint robotic manipulato
 1. **Navigate to the demo directory**:
 
    ```bash
-   cd rclnodejs/electron_demo/manipulator
+   cd rclnodejs/demo/electron/manipulator
    ```
 
 2. **Install dependencies**: