Fix html-jsx compiler

It changed React Playground to add a required props but unfortunately didn't update the call sites of the front-page. I don't think it should be required so I'm just making it optional and providing the correct default value.

Test Plan:
 - Open the front page and make sure examples are working
 - Open /react/jsx-compiler.html and make sure it is working
 - Open /react/html-jsx.html and make sure it is working
Merge pull request #698 from vjeux/fix_compiler

Fix html-jsx compiler