v0.1.1: run tests in CI, add REUSE compliance and CONTRIBUTING

- Add .github/workflows/test.yml, using flatpak-builder's run-tests
  option so PRs and pushes exercise ctest inside the same KDE SDK
  sandbox as release builds.
- Add REUSE.toml covering files that can't carry an inline SPDX header
  (.desktop, keys/*.asc).
- Add CONTRIBUTING.md documenting build/test/release steps.

io.github.toservetheking.Kareer.yml

@@ -25,11 +25,12 @@ modules:
     buildsystem: cmake-ninja
     config-opts:
       - -DCMAKE_BUILD_TYPE=Release
+    run-tests: true
     sources:
       # For Flathub / release builds, pin to a tag AND commit:
       - type: git
         url: https://github.com/toservetheking/Kareer.git
-        tag: v0.1.0
+        tag: v0.1.1
         # commit: <fill in the exact commit SHA the tag points at>
       #
       # For local testing before the repo is pushed, replace the source above with: