Add WebP support

[gjb2048]

WebP, https://en.wikipedia.org/wiki/WebP, is a more optimised web image format for web pages. See: https://www.elearningworld.org/webp/ and example code in a Moodle context: gjbarnard/moodle-format_grid@8546c57

[jarvil1]

Hello,
any progress on this? @gthomas2

[slaudel]

+1 for automatic WebP conversion
Should be relatively easy to achieve as there is a php extension: https://github.com/rosell-dk/webp-convert/

[gjb2048]

@slaudel There's already 'imagewebp' in the GD lib that Moodle uses.

[jarvil1]

https://thehackernews.com/2023/09/new-libwebp-vulnerability-under-active.html