Add ECS architecture and plugin system with source capture plugins

.gitignore

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-node_modules
+node_modules
+dist

README.md

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 # AR.js-core
 
-An attempt to convert the Ar.js threex library into an agnostic library that can be used with any 3D library.
+An attempt to convert the Ar.js threex library into an agnostic library that can be used with any 3D library.
+
+## New: ECS Architecture
+
+AR.js Core now includes a modern Entity-Component-System (ECS) architecture with a plugin system! This provides:
+
+- Modular design with a clean plugin system
+- Data-oriented ECS for efficient processing
+- Event-driven architecture with pub/sub messaging
+- Backward compatible with existing Source and Profile APIs
+
+### Quick Start with ECS
+
+```javascript
+import { Engine, CaptureSystem, SOURCE_TYPES } from "ar.js-core";
+import { webcamPlugin } from "./plugins/source/webcam.js";
+import { defaultProfilePlugin } from "./plugins/profile/default-policy.js";
+
+// Create engine and register plugins
+const engine = new Engine();
+engine.pluginManager.register(webcamPlugin.id, webcamPlugin);
+engine.pluginManager.register(defaultProfilePlugin.id, defaultProfilePlugin);
+
+// Enable profile plugin
+await engine.pluginManager.enable(defaultProfilePlugin.id, engine.getContext());
+
+// Initialize webcam capture
+await CaptureSystem.initialize(
+  {
+    sourceType: SOURCE_TYPES.WEBCAM,
+    sourceWidth: 640,
+    sourceHeight: 480,
+  },
+  engine.getContext(),
+);
+
+// Start the engine
+engine.start();
+```
+
+### Features
+
+- Core ECS: Entity-Component-System with queries and resources
+- Event Bus: Lightweight pub/sub for decoupled communication
+- Plugin System: Modular plugins for capture, tracking, and more
+- Capture System: Unified interface for webcam, video, and image sources
+- Profile Policies: Automatic device detection and performance tuning
+
+### Documentation
+
+- ECS Architecture Guide (docs/ECS_ARCHITECTURE.md) - Complete documentation
+- Minimal Example (examples/minimal/) - Working example application
+
+### Running Examples
+
+You can use either webpack (existing) or Vite (new) during development.
+
+**Webpack:**
+
+```bash
+npm install
+npm run dev
+# or watch:
+npm run dev:watch
+```
+
+**Vite:**
+
+```bash
+npm install
+npm run dev:vite
+# Opens the minimal example in your browser
+
+# Build ES module library:
+npm run build:vite
+
+# Preview build:
+npm run serve:vite
+```
+
+**Examples:**
+
+- Minimal Example: examples/minimal/index.html (Vite: http://localhost:5173/examples/minimal/index.html)
+- Image Source Example: examples/basic-ecs/image-example.html (Vite: http://localhost:5173/examples/basic-ecs/image-example.html)
+
+If the camera doesn’t start automatically, click or tap once to allow autoplay. For Safari or stricter policies, consider enabling HTTPS in `vite.config.js` (see comments in the file).
+
+## Legacy API
+
+The original Source and Profile classes are still available and fully supported:
+
+```javascript
+import { Source, Profile } from "ar.js-core";
+```
+
+See existing documentation for legacy API usage.