feat: node extension readme

Author: abose

README.md

@@ -10,6 +10,64 @@ vast npm library.
 For creating extensions that do not need node, follow this link:
 https://github.com/phcode-dev/extension-template
 
+## Setting up node extensions
+
+In package.json, add the following section
+
+```json
+{
+    "nodeConfig": {
+        "nodeIsRequired": false,
+        "main": "node/index.js",
+        "npmInstall": "node/"
+    }
+}
+```
+
+#### `nodeConfig` Object
+
+The `nodeConfig` object indicates that this is a Node extension.
+
+#### `nodeIsRequired` Field
+
+-   Set this field to `true` if the extension relies on Node and won't function
+    without it.
+-   If set to `false` or omitted, the extension can still be loaded in browser
+    versions of Phoenix code without Node support, But will use node in native
+    builds.
+-   It will be shown in the extension manager dialog in browser builds as well.
+
+#### `main` Field
+
+-   Specifies the main entry point for the Node.js component of the extension.
+-   Should point to the main JavaScript file for the Node part of the extension.
+-   Example: `"main": "node/index.js"`
+
+#### `npmInstall` Field (Optional)
+
+-   Specifies the path to run `npm install` when the user installs the extension
+    from the extension manager.
+-   It's advisable not to package `node_modules` inside the extension. Only the
+    package lock file should be distributed.
+-   Example: `"npmInstall": "node/"`
+
+## Communicating between node.js and Phoenix Code
+
+### NodeConnector-API
+
+create
+[NodeConnector-API](https://github.com/phcode-dev/phoenix/wiki/NodeConnector-API)
+to call functions and send events between your node.js and Phoenix Code
+extension components.
+
+-   This is available as a global object `global.createNodeConnector`. See above
+    link for API docs.
+-   Another API -
+    [EventDispatcher-API](https://github.com/phcode-dev/phoenix/wiki/EventDispatcher-API)
+    is also available in the global context as `global.EventDispatcher` for
+    event trigger/listen within node.
+
+# Using this template
 Follow the below 4 steps to start using this template:
 
 Refer this