Create documentation outlining steps to take for day of usability testing

[jaclinec]

We are documenting our process for planning and carrying out usability testing with users with disabilities. We already have several process documents:

• High level usability testing workflow
• General best practices for testing with people with disabilities
• Outreach and communications plan for recruiting

This Github issue is to document my creating a practical step-by-step checklist for what to do on testing day. It will be linked to the 'High level usability testing workflow' document in the first bullet above.

[jaclinec]

I finished creating the 'Testing Day Checklist' and its ready for fed final review.

[annepetersen]

Made a few edits, but otherwise looks good to me

[thisisdano]

Done!