[Meta] Improve accessibility of Open Social, so it conforms to WCAG2.0 AA

Just tagging this. Thanks @basvanos

Thanks Bas for creating this inventory of accessibility issues. I will ask @maikelkoopman to go through the list to see what the low hanging fruit is.

For items that are harder to solve we might need to create some child issues. Is that ok with you?

Just let me share my thoughts on the first item about images an Alternative text.

For posts with a photo the filename is used for all other images (f.e preview images of topics and events in streams) no Alternative text shows up, if not specified.
The Alt-text field is not required in Open Social.

If you run a website, where editors insert the content you can force them to specify an Alternative text by simply making the field required.
But for sites like Communities, Portals, Intranets - at the end all sites with user generated content - forcing the users to specify an Alternative text will lead through less engagement.

One thing possible today is using a Cognitive service that can "look at" and describe the image. This describtion can than be used to generate the Alternative text. But these services offered f.e. by Google or Microsoft need an additional registration (and payment) and can't be bundled with a distribution like Open Social for free or on an automatic install.

I played around last days an came up with: https://www.drupal.org/project/auto_alter

After module is enabled and configured, it automatically creates Alternative Texts for images, when a user did'nt specify one.
To add this module to Open Social (disabled) would be easy. But to make use of it, the enduser needs to register at Micrsoft Azure for using the service.

I find this a really nice W3C starter guide for locking in the accessibility fundamentals

Easy Checks - A First Review of Web Accessibility

I've got a simple audit spreadsheet that I use for this type of audit - it might be useful for the team - I'll share in slack - I don't have a google doc version

Another easy starting point is just running your site through http://wave.webaim.org/extension/

This is useful for both the public & admin pages of your site.

Is this a meta issue for Open Social and accessibility? Would that be useful to coordinate?

Fun fact: the verb "to comply" doesn't appear anywhere in WCAG. It uses the term conformance.

This is still relevant for current versions of Open Social. I've updated the issue summary to contain an overview of open and closed tickets. Somewhat easier to grok than the list of child issues.

Added #3175829: It's unclear that dropdown menu items are expandable