feat: create readme for CoAP binding package

packages/binding-coap/README.md

@@ -0,0 +1,90 @@
+# CoAP Protocol Binding of node-wot
+
+## Getting Started
+
+In the following examples it is shown how to use the CoAP binding of node-wot.
+
+### Prerequisites
+* `npm install @node-wot/core`
+* `npm install @node-wot/binding-coap`
+
+### Client Example
+
+The client example tries to connect to a TestThing via CoAP and reads a property `string`. The ThingDescription is located under the follwing CoAP uri coap://plugfest.thingweb.io:5683/TestThing.
+
+`node example-client.js`
+
+```
+// example-client.js
+Servient = require("@node-wot/core").Servient
+CoapClientFactory = require("@node-wot/binding-coap").CoapClientFactory
+
+Helpers = require("@node-wot/core").Helpers
+
+// create Servient and add CoAP binding
+let servient = new Servient();
+servient.addClientFactory(new CoapClientFactory(null));
+
+let wotHelper = new Helpers(servient);
+wotHelper.fetch("coap://plugfest.thingweb.io:5683/TestThing").then(async (td) => {
+    // using await for serial execution (note 'async' in then() of fetch())
+    try {
+        servient.start().then((WoT) => {
+            WoT.consume(td).then((thing) => {
+                // read a property "string" and print the value
+                thing.readProperty("string").then((s) => {
+                    console.log(s);
+                });
+            });
+        });
+    } catch (err) {
+        console.error("Script error:", err);
+    }
+}).catch((err) => { console.error("Fetch error:", err); });
+```
+
+### Server Example
+
+The server example produces a thing that allows for setting a property `count`. The thing is reachable through CoAP. Additional additional handlers could be added.
+
+`node example-server.js`
+
+```
+// example-server.js
+Servient = require("@node-wot/core").Servient
+CoapServer = require("@node-wot/binding-coap").CoapServer
+
+Helpers = require("@node-wot/core").Helpers
+
+// create Servient add HTTP binding
+let servient = new Servient();
+servient.addServer(new CoapServer());
+
+servient.start().then((WoT) => {
+    WoT.produce({
+        "@context": "https://www.w3.org/2019/wot/td/v1",
+        title: "MyCounter",
+        properties: {
+			count: {
+				type: "integer"
+            }
+        }
+    }).then((thing) => {
+        console.log("Produced " + thing.title);
+        thing.writeProperty("count", 0)
+
+        thing.expose().then(() => {
+            console.info(thing.title + " ready");
+            console.info("TD : " + JSON.stringify(thing.getThingDescription()));
+            thing.readProperty("count").then((c) => {
+                console.log("cound is " + c);
+            });
+        });
+    });
+});
+```
+
+
+### More Details
+
+see https://github.com/eclipse/thingweb.node-wot/