added example files

.env.example

+# BigBlueButton Server url:
+BBB_URL=https://your_BigBlueButton_server/bigbluebutton/api
+# BigBlueButton secret:
+BBB_SECRET=your_secret
+# BigBlueButton meetingID:
+BBB_MEETING_ID=your_meetingID
+# Media server url:
+BBB_STREAM_URL=rtmp://media_server_url/stream/stream_key

docker-compose.yml

+version: '3.3'
+services:
+  bbb-streamer:
+    container_name: liveStreaming
+    env_file: .env
+    build: 
+        context: ./

docker-compose.yml.example

+version: '3.3'
+services:
+  bbb-streamer:
+    image: aauzid/bigbluebutton-livestreaming
+    container_name: liveStreaming
+    environment:
+      # BigBlueButton Server url:
+      - BBB_URL=https://your_BigBlueButton_server/bigbluebutton/api
+      # BigBlueButton secret:
+      - BBB_SECRET=your_secret
+      # BigBlueButton meetingID:
+      - BBB_MEETING_ID=your_meetingID
+      # Media server url:
+      - BBB_STREAM_URL=rtmp://media_server_url/stream/stream_key