add Public_url in build scripts of microfrontend

Author: prafull-opensignlabs

microfrontends/SignDocuments/package.json

@@ -36,7 +36,7 @@
   },
   "scripts": {
     "start": "mf-cra start",
-    "build": "CI=false && BUILD_PATH='./mfbuild' mf-cra build && mv mfbuild ../../apps/OpenSign/public",
+    "build": "CI=false && PUBLIC_URL=./mfbuild BUILD_PATH='./mfbuild' mf-cra build && mv mfbuild ../../apps/OpenSign/public",
     "test": "react-scripts test",
     "eject": "react-scripts eject"
   },