Add gitea as git-server to k8s-cluster

By applying this change the kubernetes cluster gets a gitea-server
setup. Note, that I use a custom-image which I have to automate in
future. The customization is necessary since I use asciidoc very often
and the default-gitea doesn't render these files, so it becomes a bit
cumbersome to read them on the web.

roles/k8s-setup/tasks/main.yml

@@ -3,3 +3,9 @@
   - k8s
   - cert-manager
   import_tasks: _cert-manager.yml
+
+- name: Ensure gitea
+  tags:
+  - k8s
+  - gitea
+  import_tasks: _gitea.yml