Tito 0.6.23

• Use SPDX License
• Don't upload .patch files into a DistGit lookaside cache, they should only be committed to git
• Add Tito's mascot and writeup of the project history
• Don't override packit.yaml in DistGit repository
• Fix #454 - Replace submodule--helper list with git config --get-regexp
• Fix #456 - Transitive submodule resolution

Thank you @xsuchy, @praiskup, @frenzymadness, and @arcivanov for contributing to this release.