Update README.md

```compile``` is deprecated and should be replaced with ```implementation```

README.md

@@ -182,7 +182,7 @@ Then add the dependency to your module's build.gradle:
 
 /app/build.gradle
 ```groovy
-compile 'com.github.felHR85:UsbSerial:4.5.2'
+implementation 'com.github.felHR85:UsbSerial:4.5.2'
 ```
 
 TO-DO