define typings of publish and publishUnsafe more precisely. Resolves #…

…131.

.gitignore

@@ -5,6 +5,7 @@ src/**/*.js
 src/**/*.d.ts
 src/**/*.metadata.json
 package-lock.json
+.idea
 *.map
 *.js
 *.d.ts

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ngx-mqtt",
-  "version": "6.8.5",
+  "version": "6.9.0",
   "description": "ngx mqtt client library",
   "main": "bundles/ngx-mqtt.min.js",
   "module": "./src/index.js",

src/mqtt.service.ts

@@ -220,7 +220,7 @@ export class MqttService {
    * the observable will emit an empty value and completes, if publishing was successful
    * or throws an error, if the publication fails.
    */
-  public publish(topic: string, message: any, options?: IPublishOptions): Observable<void> {
+  public publish(topic: string, message: string | Buffer, options?: IPublishOptions): Observable<void> {
     if (!this.client) {
       throw new Error('mqtt client not connected');
     }
@@ -241,7 +241,7 @@ export class MqttService {
    * This method publishes a message for a topic with optional options.
    * If an error occurs, it will throw.
    */
-  public unsafePublish(topic: string, message: any, options?: IPublishOptions): void {
+  public unsafePublish(topic: string, message: string | Buffer, options?: IPublishOptions): void {
     if (!this.client) {
       throw new Error('mqtt client not connected');
     }