Update README.md

adding the necessary conda add channel command in the quickstart

README.md

@@ -45,7 +45,8 @@ Ready to dig into it ? In a few lines you can install **Spleeter** using [Conda]
 
 ```bash
 # install using conda
-conda install -c conda-forge spleeter
+conda config --add channels conda-forge # only needed if you don't already have this channel set
+conda install -c deezer-research spleeter 
 # download an example audio file (if you don't have wget, use another tool for downloading)
 wget https://github.com/deezer/spleeter/raw/master/audio_example.mp3
 # separate the example audio into two components