using js-to-ts converter on JSX. (#3906)

Added 'include' parameter to tsconfig to tell the compiler to only look inside the src directory

packages/slate-hyperscript/test/fixtures/element-empty.tsx

@@ -0,0 +1,7 @@
+/** @jsx jsx */
+import { jsx } from 'slate-hyperscript'
+
+export const input = <element />
+export const output = {
+  children: [],
+}