Bug - Content Editor WYSIWYG - Add visible element for HTML Block

[kodster28]

Description

As a follow-up to #1215, would be helpful to have the HTML Block available via a button in the WYSIWYG editor (as well as the /html shortcut).

Broadly, also wouldn't be the worst idea to figure out a pattern to surface all the shortcut commands somehow, those will get missed as folks onboard onto the system.

Steps to reproduce

n/a

Environment

• emdash: 0.17.0
• Cloudflare Workers
• MacOS / Chrome

Logs / error output

[emdashbot]

The investigation bot ran into a problem and could not complete.

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_{Run: https://github.com/emdash-cms/emdash/actions/runs/27008284615}