Add SVG to initial comment linking to dashboard

[xmo-odoo]

alt img src seems to work with svgs?

• state (from mergebot POV)
• linked PRs
• direct links (to what?)

Maybe dupe the state table from #771?

After some experimentations:

• external CSS and fonts don't work in image mode so needs an embedded fallback for that
• because github sets CSP default-src: 'none' and no style-src, even internal <style> blocks don't work with uploaded, although it ought work if the <img> links to the mergebot, then again is linking to the SVG really useful vs linking to the actual page? Probably not.
• image-svg are completely uninteractive, notably links don't work
• size of SVG is a bit of a pain in the black art
• github caches linked images, caching policy (and possibly how it respects cache headers) has not been determined, although it definitely doesn't seem to care about a query string

Demo with odoo/odoo#110369 (https://mergebot.odoo.com/odoo/odoo/pull/110369):

actual link:

edit: looks like the cache configuration is such that after taking the dev server down github just removes the entire thing, noice

[xmo-odoo]

Definitely depends on #771 (as it's basically adding that one's information in an other location), which itself depends on #789.

Also likely useful reading for when I tackle this: https://www.nan.fyi/svg-paths (so I don't lose / forget about it)