added ffmpeg into docker

Dockerfile

@@ -5,8 +5,15 @@ WORKDIR /app
 # We copy our package.json file to our
 # app directory
 COPY package.json /app
+
+
+RUN apt-get update \
+    && apt-get clean \
+    && apt-get install -y ffmpeg
+
 # We then run npm install to install
 # express for our applicationRUN 
+
 RUN npm install
 # We then copy the rest of our application
 # to the app direcoty