[change] Add usePlatformMethods to implement instance methods

A hook equivalent for implementing "native methods" on refs to elements backed
by function components.

scripts/jest/setupFiles.js

@@ -0,0 +1,10 @@
+/* eslint-env jasmine, jest */
+
+// JSDOM doesn't implement ResizeObserver
+class ResizeObserver {
+  disconnect() {}
+  observe() {}
+  unobserve() {}
+}
+
+window.ResizeObserver = ResizeObserver;