Add a guide for alt text

[dmundra]

Are guide is lacking some directions for alt text, we could write a few paragraphs and then link to resources:

• https://www.tpgi.com/what-is-alt-text-and-how-to-write-it/
• https://design.va.gov/content-style-guide/alternative-text-for-images
• https://webaim.org/techniques/alttext/
• https://www.w3.org/WAI/tutorials/images/decision-tree/

[MarcusMorba]

@dmundra & @mgifford - is this issue still relevant? Where should the guide be included?

[dmundra]

I guess it would go under https://accessibility.civicactions.com/guide/

[MarcusMorba]

Thanks. Will start to prepare a draft after sept. 8th. Please stay patient.