signature-verification: accommodate changes in cosign cli behavior and add tldr

[mohammed90]

TODO:

• [ ] Figure out how to fetch UUID of tlog entry using cosign to retain the multi-perspective verification

This is how the tldr looks

Closes #312

[francislavoie]

I'd maybe add spaces in front of each line of the command for alignment, similar to https://caddyserver.com/docs/running#usage