added missing openlayers types as dev dependency

package.json

@@ -32,6 +32,7 @@
     "@types/lodash": "^4.14.135",
     "@types/node": "11.13.7",
     "@typescript-eslint/eslint-plugin": "~1.4.2",
+    "@types/ol": "^6.3.1",
     "@vue/test-utils": "^1.0.0-beta.31",
     "eslint": "~5.15.1",
     "eslint-config-prettier": "~4.1.0",