deps: update eslint

This is required due to the Babel update.

package.json

@@ -97,13 +97,13 @@
     "babel-loader": "8.0.4",
     "clean-css": "3.4.25",
     "css-loader": "0.28.7",
-    "eslint": "4.12.1",
+    "eslint": "5.6.1",
     "eslint-config-jitsi": "github:jitsi/eslint-config-jitsi#7474f6668515eb5852f1273dc5a50b940a550d3f",
-    "eslint-plugin-flowtype": "2.39.1",
-    "eslint-plugin-import": "2.8.0",
-    "eslint-plugin-jsdoc": "3.2.0",
-    "eslint-plugin-react": "7.5.1",
-    "eslint-plugin-react-native": "3.2.0",
+    "eslint-plugin-flowtype": "2.50.3",
+    "eslint-plugin-import": "2.14.0",
+    "eslint-plugin-jsdoc": "3.8.0",
+    "eslint-plugin-react": "7.11.1",
+    "eslint-plugin-react-native": "3.3.0",
     "expose-loader": "0.7.4",
     "file-loader": "1.1.5",
     "flow-bin": "0.67.1",