Add web accessibility tools for users

[yucheng11122017]

Please confirm that you have searched existing issues in the repo

Yes, I have searched the existing issues

Any related issues?

No response

What is the area that this feature belongs to?

Reader Usability

Is your feature request related to a problem? Please describe.

Would be good to include tools to help users enhance the accessibility of their website.

Describe the solution you'd like

We can include web accessibility tools to help detect and fix accessibility problems for example Axe as used by Teammates currently.

Describe alternatives you've considered

Other accessibility tools could be explored as well!

Additional context

No response

[damithc]

Good suggestion @yucheng11122017 I guess one thing to ensure first is that MarkBind does not make content 'less accessible' on our own accord e.g., use default color combinations that don't have enough contrast

[yucheng11122017]

Thats a good idea Prof! Some things from examining our user guide for now

• Certain formatting results in lack of contrast eg. grey text, inline code, links
• General improper structure of html eg. Page nav is not formatting correct because <ul> contains a <div> than <li> element
• Missing aria-labels in buttons and links
• Missing lang attributes
• Missing alt text in images

For now, it seems the lack of contrast is the biggest violator in general. I will make a PR for now just to correct some of these mistakes if possible and then later look into adding web accessibility tools in Markbind for users to use. :)