Run quickstart with JS sdk; 在 quickstart 中添加 Javscript demo

[seeflood]

What would you like to be added:
Currently users can run Layotto quickstart with Java sdk, which is friendly for Java developers who don't have golang environment on their laptop. See https://mosn.io/layotto/#/en/start/state/start

Next, we need to make the quickstart demos more friendly to Javascript users by adding an option to run with Javascript:

We already have js-sdk and examples at https://github.com/layotto/js-sdk . So this issue needs us to improve js demos and Layotto quickstart docs.

Why is this needed:
#67