docs: add alt text to all images for accessibility

[VerisimilitudeX]

Overview: What does this pull request change?

Add alt text to all images for improved accessibility

Motivation and Explanation: Why and how do your changes improve the library?

Individuals utilizing screenreaders may face difficulty while accessing this tool due to the current lack of alt text for the badge glyphs. This PR fixes that.

Links to added or changed documentation pages

README.md

Further Information and Comments

N/A

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested

[VerisimilitudeX]

@frafra @mrdon @shalunov @shalunov @charliepark could you please take a look?

[frafra]

@VerisimilitudeX why? I am not a reviewer nor maintainer, so please avoid spamming notifications. I hope your PR gets accepted :)

[VerisimilitudeX]

Apologies, @frafra. I’ll keep that in mind.

[VerisimilitudeX]

@PgBiel would you like me to make any modifications to this PR?