[WIP] showcase: add Prism

[fenekku]

:warning: Let @carsonicator review before merging.

Description

Add Prism to the showcase section. Here is what it looks like:

An alternative was tried with a fullpage screenshot but it felt too long:

Checklist

Ticks in all boxes and 🟢 on all GitHub actions status checks are required to merge:

• [x] I'm aware of the code of conduct.
• [x] I've created logical separate commits and followed the commit message format.
• [x] I've added relevant test cases.
• [x] I've added relevant documentation.
• [x] I've marked translation strings (for relevant code).
• [x] I've followed the CSS/JS and React guidelines (for relevant code).
• [x] I've followed the web accessibility guidelines (for relevant code).
• [x] I've followed the user interface guidelines (for relevant code).
• [x] I've identified the copyright holder(s) and updated copyright headers for touched files (>15 lines contributions).
• [x] I've NOT included third-party code (copy/pasted source code or new dependencies).

Third-party code

If you've added third-party code (copy/pasted or new dependencies), please reach out to an architect.

Reminder

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1. You license your contribution under the same terms as the current repository’s license.
2. You agree that you have the right to license your contribution under the current repository’s license.

[kristiholmes]

How do I best suggest an edit to the description?

[carsonicator]

@kristiholmes You can add a suggestion in this comment section.

[fenekku]

Adding suggestions on the "Files Changed" tab is probably the easiest. The current description comes from https://galter.northwestern.edu/galterguides?url=https://libguides.galter.northwestern.edu/prism .