chore: add web components base peer dependency

Author: MarcusNotheis

packages/main/package.json

@@ -33,6 +33,7 @@
   },
   "peerDependencies": {
     "@ui5/webcomponents": "1.0.0-rc.6",
+    "@ui5/webcomponents-base": "0.19.0",
     "@ui5/webcomponents-fiori": "1.0.0-rc.6",
     "@ui5/webcomponents-icons": "1.0.0-rc.6",
     "react": "^16.8.0",