add appveyor cache (#20490)

Summary:
add appveyor cache for better build speed.
pass all current ci.
none
 [GENERAL] [INTERNAL] [CI] - add appveyor cache
Pull Request resolved: https://github.com/facebook/react-native/pull/20490

Differential Revision: D9128396

Pulled By: hramos

fbshipit-source-id: a973f73455b28b8eec002cc28f7eb2f6d8302b9c

appveyor.yml

@@ -40,3 +40,9 @@ build_script:
 
 test_script:
     - npm test
+
+cache:
+  - node_modules
+  - "%LOCALAPPDATA%/Yarn"
+  - "%USERPROFILE%/.gradle/caches"
+  - "%USERPROFILE%/.gradle/wrapper"