guides: Add flatpak signature guide
This commit adds a user guide explaining how to create flatpaks signed with the Ed25519 algorithm, and how to verify such flatpaks.
🟠 v2026dev0 entered Soft Code Freeze/Hard Feature Freeze, only bug fixes will be accepted • schedule
This commit adds a user guide explaining how to create flatpaks signed with the Ed25519 algorithm, and how to verify such flatpaks.