New workflow + spring cleaning

- Workflows must be present in the master branch to be available to run
  from other branches
- Removing the codeowners file as most of the people don't work here
  and/or aren't involved with the project anymore

.github/workflows/container-image.yml

@@ -0,0 +1,12 @@
+name: Container image
+
+on:
+  workflow_dispatch:
+
+jobs:
+  hello_world:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Hello World step
+      run: echo "hello world"