[Feature request] Support WEBP as image format in newsletters

[MMachado05]

Keila currently seems only to support .JPG and .PNG files for putting images in newsletters. Seeing as it's seeing continued frequent use, adding .WEBP support as well will make the image-uplading experience on Keila much smoother!

[wmnnd]

Thank you for suggesting this, you're absolutely right we should add WebP.

However, please note that many email clients still don't support the format so I would generally advise against using it in newsletters:
https://www.caniemail.com/search/?s=webp