Develop example Accordion

[jnurthen]

Change background image for expand collapse to something that works in high contrast mode

[jnurthen]

@accdc

[ZoeBijl]

Which branch is this in?

[accdc]

I think we are waiting for Matt to insert the code into the template after his code review.

[mcking65]

I added a first draft of the design pattern and integrated Bryan's example code in commit 1ecb9be.

I published it in the master branch, so it can be viewed at:
http://w3c.github.io/aria-practices/#accordion

[mcking65]

From August 29, 2016 meeting of APG task force, @jnurthen will remove web fonts and adjust colors .

[carmacleod]

This example has an almost-black background, which makes it almost impossible to read.
The problem is the body style:
background-color: #2E3135;
in file global.css, line 41.
If I completely delete that style, then the example page has a white background, which is way better.