feat(listen() & shutdown() methods): Optional callbacks were added to these 2 methods

Optional callbacks were added to `listen()` & `shutdown()` methods to consumer be able to handle
events even without `then()` method.

Author: mirismaili

README.md

@@ -69,10 +69,11 @@ npm install simplatic-http-server
 	const staticServer = new StaticServer(portNumber /*, servePath = process.cwd() */) 
 	```
 
-3. Listen to a port:
+3. Listen to `portNumber`:
 
 	```js
-	await staticServer.listen()
+	await staticServer.listen(/* onListenCallback, onErrorCallback */)
+
 	console.log(`The static server listening on ${portNumber} ...`)
 	```
 
@@ -85,10 +86,10 @@ npm install simplatic-http-server
 	)
 	```
 
-4. Get access to a file in `servePath`. E. g: type in your browser's address bar: `http://127.0.0.1/dir/index.html`. *Note: The path of `index.html` must be `` `${servePath}/dir/index.html` `` on your local machine.*
+4. Get access to a file in `servePath`. E. g. type in your browser's address bar: `http://127.0.0.1/dir/index.html` *(Note: The path of `index.html` must be `` `${servePath}/dir/index.html` `` on your local machine).*
 
 5. Turn it off when no more needed:
 
 	```js
-	await staticServer.shutdown()
+	await staticServer.shutdown(/* callback */)
 	```

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "simplatic-http-server",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "description": "A very light-weight and very simple static HTTP server based on node's built-in http module",
   "main": "dist/main.umd.js",
   "types": "dist/types/main.d.ts",

package.json

@@ -5,6 +5,7 @@ import http from 'http'
 
 import debug from 'debug'
 
+// noinspection JSUnusedGlobalSymbols
 /**
  * Created at 1398/4/2 (2019/6/23).
  * @author {@link https://mirismaili.github.io S. Mahdi Mir-Ismaili}
@@ -53,18 +54,32 @@ export default class StaticServer {
 		})
 	}
 
-	listen(): Promise<void> {
+	// noinspection JSUnusedGlobalSymbols
+	listen(onListen: () => void = () => {}, onError: (err: Error) => void = () => {}): Promise<void> {
 		return new Promise((resolve, reject) => {
-					this.staticServer.on('error', reject)
-					
-					this.staticServer.listen(this.port, resolve)
-				}
-		)
+			try {
+				this.staticServer.on('error', err => {
+					onError(err)
+					reject(err)
+				})
+				
+				this.staticServer.listen(this.port, () => {
+					onListen()
+					resolve()
+				})
+			} catch (err) {
+				onError(err)
+				reject(err)
+			}
+		})
 	}
 
-	shutdown(): Promise<void> {
+	shutdown(callback: (err?: Error) => void = () => {}): Promise<void> {
 		return new Promise((resolve, reject) =>
-				this.staticServer.close(err => err === undefined ? resolve() : reject(err))
+				this.staticServer.close(err => {
+					callback(err)
+					err === undefined ? resolve() : reject(err)
+				})
 		)
 	}
 }