(feat) Img component

[hestonhoffman]

Adds Img component with support for images and videos.

• ImgVideo is a child of Img
• Images use CDN links instead of loading from repo. Local dev + staging use the staging URL. Prod uses prod.
• Added a lightbox to replicate behavior on Hugo.
• Added a plaintext twin that renders an img tag with the prod src, caption, and alt text. For inline images, it drops the tag. I decided to just grab the prod source for the image here instead of rendering the path for each environment. I don't think we gain much from rendering the local path in local etc.
• I removed image properties that appear to be dead in Hugo (href, target, wide, img_param, pop_param, figure_class, and figure_style).
• I replaced the style prop with widthPercent and added a validation error that prevents writers from using widthPercent with height/width.

🟢 All tests pass
🟢 You can preview this using preview or dev now, since they use the same URL.