Initial plugin runtime api implementation

test/resources/plugin/test-plugin/test.js

@@ -0,0 +1,13 @@
+module.exports = function(RED) {
+    console.log("Loaded test-plugin/test")
+
+    RED.plugins.registerPlugin("my-test-plugin", {
+        type: "foo",
+        onadd: function() {
+            console.log("my-test-plugin.onadd called")
+            RED.events.on("registry:plugin-added", function(id) {
+                console.log(`my-test-plugin: plugin-added event "${id}"`)
+            });
+        }
+    })
+}