Add PUBLIC_URL to network-explorer

Apparently webpack devserver needs also PUBLIC_URL to be defined

Author: Tuomas Koponen

docker-compose.yml

@@ -258,6 +258,7 @@ services:
             retries: 60
         stdin_open: true
         environment:
+            PUBLIC_URL: "/network-explorer"
             REACT_APP_BASENAME: "/network-explorer"
             REACT_APP_STREAMR_API_URL: "${STREAMR_BASE_URL}/api/v1"
             REACT_APP_TRACKER_REGISTRY_PROVIDER: "${STREAMR_BASE_URL}/mainchain-rpc/http/"