Check alt tags for images

[LeandraH]

Is your feature request related to a problem? Please describe. We should have an alt tag for all images that we show, otherwise a screenreader might e.g. read out the server address that the image is saved at. If the image doesn't contain useful information, we should have an empty string as alt tag.

Describe the solution you'd like

• If an image in the remote content doesn't have an alt tag, we should give it an empty string.
• For our icons on buttons, e.g. the search one, we should have an empty alt tag and handle the description of the action in the button around it, so a screenreader should read "search" for the button and not "magnifying glass" for the icon.
• If we have other icons that are not buttons (I can't think of any), we should think about whether they have a function that we want a screenreader to say. Maybe testing with a screenreader would be a good idea for that.

[svenseeberg]

https://www.w3.org/WAI/tutorials/images/decorative/ and https://www.w3.org/WAI/tutorials/images/informative/ provide more context.

[svenseeberg]

• Maybe testing with a screenreader would be a good idea for that.

I just tested Pericles (Firefox Addon) and did not have any problems in the web app.