docs: add video caption contribution guide to accessibility page

[awen11123]

Summary

Add a short guide to the accessibility page encouraging community members to help improve video captions. This is especially useful during collaborative events like the Smörgåsbord.

Changes

• accessibility.md: add a new "Help Improve Our Video Captions" section with step-by-step instructions for editing auto-generated captions.

Co-Authored-By: Claude noreply@anthropic.com

[shiltemann]

Thanks @awen11123! I don't think its so useful to share the link to the folder, there is rarely anything there to do, and we always get the speakers to fix up their own video captions.

So maybe you can phrase it more generally like "if you record a video, you will be sent a link to a captions document, ..."

This does make me think that maybe we should save the captions somewhere on the GTN so that people can fix any mistakes in them after they are already added to the video. Let me have a think about that, thanks for raising the point :)

[shiltemann]

oh, and please add yourself to our CONTRIBUTORS.yaml file :)

[awen11123]

Thanks for the feedback @shiltemann!

I've updated the section:

• Removed the folder link and rewrote the guide to focus on the speaker workflow (receive a captions doc → review and correct)
• Added a note that the GTN is exploring ways to let the community help improve existing captions — looking forward to seeing what comes of that!

Also added myself to CONTRIBUTORS.yaml :)