Revert "Remove unused Courgette PNG files."

This reverts commit 4af8f6c.

Reason for revert: The images seem to be still used by the md and html files, but just named incorrectly.

Original change's description:
> Remove unused Courgette PNG files.
>
> Bug: 1257736
> Change-Id: I4a5d2cbb033bec6a3966cb49824b6ca762fcb989
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3232667
> Auto-Submit: Addison Luh <aluh@chromium.org>
> Commit-Queue: Will Harris <wfh@chromium.org>
> Reviewed-by: Will Harris <wfh@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#933185}

Bug: 1257736
Change-Id: Ia64996aa8e36f6b24500996313f6f54d38537e01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3292368
Auto-Submit: Addison Luh <aluh@chromium.org>
Commit-Queue: Will Harris <wfh@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#943623}