frontend: use webp thumbnails

[SamuelPull]

Checklist

• [x] I have followed (at least) the PR section of the contributing guide.
• [x] I fixed all necessary PR warnings
• [x] The commit history is clean
• [x] The E2E tests are passing
• [x] If possible, the issue has been divided into more subtasks
• [x] I did a self review before requesting a review from another team member

Description

How to test

You might need to rebuild frontend container image

Closes #1753

[github-actions[bot]]

	Warnings
:warning:	No CHANGELOG added.
:warning:	There were changes in the frontend, but no E2E-test was added or modified!

Generated by :no_entry_sign: dangerJS against 25157ca4bd489a34c4e15fe23c5f6a3c8ea68a49

[openkfwCI]

	Notes	Time
:x:	Note for Reviewer: E2E tests on pipeline 58415 on remote server failed	Tue, 09 Apr 2024 06:16:29 +0000

Generated by E2E-Test