updates to hw3.

Overview

This PR makes changes to HW2, and leaves some to-dos and questions for Jen.

description of changes

• added a small component to be consistent with using skils they already learned to the participation score. Can we adopt this for all homeworks?
• updated optional reading. the race plus alt-text paper did not feel like the most appropriate because we are saying they may be practicing UI descriptions. linked to a UDescribe instructional video that models ui descriptions.
• Updated description of second AT under subheading Collect Data on accessibility problems
• updated turn-in.

to-dos

for @khanna38

• Review changes, website pages, and fix any issues.
• modify accessible document creation rubric on canvas with information about violations. Please let me know if you have any questions.
• mark this PR ready but do not merge after you are done with the to-dos.

questions for @jmankoff

• point to definitions for terms of frequency, impact and persistence. what would be a good link to include?
• unable to find cosmetic definition for civerity in the article you suggested. I however found another article and updated the doc. Is this ok?
• rubric "Comfortable Applying Web/App Accessibility Rules": only the first rating does not have a count such as one or more... how do we grade for "Correctly assigns from WCAG guideline areas to all found problems (or says if they are not applicable) and demonstrates understanding of guideline areas" and "Correctly draws from at least two WCAG guideline areas and assigns to all problems"?
• "Accessibility Problem Fixes" may not be applicable to this homework. Should we remove it? I reviewed the spec after our chat conversation but couldn't find a suggestion to improve. I may have missed something though but I wanted to bring this to your attention again.
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