Link preview malformed

[JonathanOppenheimer]

Currently, due to the direct use of the readme for link previews, sending someone https://www.sigstore.dev/ results in a malformed preview description.

For example, when sending someone the URL on Discord, the following behavior is observed:

Similar behavior can be observed here.

The text being pulled is here in the readme.

I would suggest the use of of meta tags, if possible, so the preview reads "Sign, verify and protect your software" as intended.