Fixed prettier nullish chaining bug (#120)

In the `@react-native-community/eslint-config` package a quite outdated version of prettier is used which does not support the nullish chaining yet. While adding prettier to the devDependencies, this bug is fixed.

template/App.tsx

@@ -46,8 +46,8 @@ const App = () => {
             <View style={styles.sectionContainer}>
               <Text style={styles.sectionTitle}>Step One</Text>
               <Text style={styles.sectionDescription}>
-                Edit <Text style={styles.highlight}>App.tsx</Text> to change this
-                screen and then come back to see your edits.
+                Edit <Text style={styles.highlight}>App.tsx</Text> to change
+                this screen and then come back to see your edits.
               </Text>
             </View>
             <View style={styles.sectionContainer}>

template/package.json

@@ -16,9 +16,9 @@
   "devDependencies": {
     "@babel/core": "^7.6.2",
     "@babel/runtime": "^7.6.2",
-    "@react-native-community/eslint-config": "^0.0.5",
+    "@react-native-community/eslint-config": "^0.0.7",
     "@types/jest": "^24.0.24",
-    "@types/react-native": "^0.60.25",
+    "@types/react-native": "^0.61.15",
     "@types/react-test-renderer": "16.9.1",
     "@typescript-eslint/eslint-plugin": "^2.12.0",
     "@typescript-eslint/parser": "^2.12.0",
@@ -27,6 +27,7 @@
     "jest": "^24.9.0",
     "metro-react-native-babel-preset": "^0.56.0",
     "react-test-renderer": "16.9.0",
+    "prettier": "^1.19.1",
     "typescript": "^3.7.3"
   },
   "jest": {