Add missing doctor descriptions

[cortinico]

Summary:

I've noticed that some of our doctor inspections are missing labels. I've added the missing ones:

Common
 ✓ Node.js
 ✓ yarn
 ✓ Watchman - Used for watching changes in the filesystem when in development mode

Android
 ✓ JDK
 ✓ Android Studio - Required for building and installing your app on Android
 ✓ Android SDK - Required for building and installing your app on Android
 ✓ ANDROID_HOME

iOS
 ✓ Xcode - Required for building and installing your app on iOS
 ✓ CocoaPods - Required for installing iOS dependencies
 ✓ ios-deploy - Required for installing your app on a physical device with the CLI
 ✓ .xcode.env - File to customize Xcode environment

Test Plan:

Not sure how to test this as that's mostly string changes

[thymikee]

Thanks!

[thymikee]

We should make description mandatory in typedef. cc @szymonrybczak