add basic ci-like workflow

[spamviech]

steps:

• checkout
• install toolchain (+ cargo outdated)
• setup cache
• check format
• build
• test
• clippy
• cargo-outdated

[github-actions[bot]]

Please complete the following tasks before merging this PR:

• [x] update dependencies (cargo update + check cargo outdated)
• [x] update licenses folder
  • clean current licenses
  • run fetch_licenses.py
  • commit result
  • check test output if licenses are up to date
• [x] update Changelog.md, so all included changes appear under the section
• [x] update zugkontrolle.desktop