The GitHub blog post for job Summaries mentions the ability to use markdown for a job's step summary. If you follow the documentation link in the post it states that...
Job summaries support GitHub flavored Markdown, and you can add your Markdown content for a step to the GITHUB_STEP_SUMMARY environment file.
This would imply images are supported, but when I try  the alternate text is showed as a working link to the image.
relative_path == "./process/assets/inactive.png"
Is it possible to display an image in a GitHub workflow step summary?
For reference: GitHub Flavored Markdown Spec