Write a study JSON & YAML example

[hesyifei]

Probably two local files like this:

wellping/src/helpers/studyFile.ts

Lines 13 to 15 in e22f452

	export const WELLPING_LOCAL_DEBUG_URL =
	"https://wellping_local__.ssnl.stanford.edu/debug.json";
	// TODO: export const WELLPING_LOCAL_DEMO_URL = "https://wellping_local__.ssnl.stanford.edu/demo.json";

This way we can have a debug study file that can be modified during development while also having a demo study file that everyone can easily use (without having to set up a server or writing a study file) to see how the app works.

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Update 2022-05-28: We now have some example study files at https://wellping.github.io/example-study-files/. But we probably also want a template study file in YAML and one in JSON (which can just be converted from YAML).