Treat images as figures by default, and add a border etc

[chalin]

After investigating

• Add a frame border to an image #2271

I came to realize that most images (95+%) in the website pages could benefit from a border.

Content authors often embed figures as images in pages, like this:

opentelemetry.io/content/en/blog/2023/jmx-metric-insight/index.md

Line 150 in 7acee87



IMHO, the main "use case" of an image in markdown is as an embedded figure as illustrated above. As such, images should be treated as block elements and always have a border by default.

This could be addressed by defining an image render hook that actually encodes an image as a figure, or possibly just some styling defaults.

[chalin]

Image reference hook resources:

• https://discourse.gohugo.io/t/not-able-to-render-images/42948/4
• https://discourse.gohugo.io/t/pass-attributes-to-image-render-hook/36899

[chalin]

As a possible followup to #2359, it might be good to generalize the class name img-initial to, say, otel-initial so that it can be more broadly used. Cf. google/docsy#1431