Add Docker and Gitea workflow configurations for Talks slides deployment

- Introduced .dockerignore to exclude unnecessary files from Docker builds.
- Added build-and-push.yaml workflow for automated image building and Helm chart deployment on changes to specific paths.
- Created Dockerfile for building a static site with Nginx, including configuration for serving slides.
- Established Helm chart structure in talks-slides-dist for managing deployment configurations and resources.
- Removed outdated GitHub Actions workflows to streamline CI/CD processes.

talks-slides-dist/Chart.yaml

@@ -0,0 +1,11 @@
+apiVersion: v2
+name: talks-slides-chart
+description: Helm chart for Talks slides (Nginx + contenu git)
+type: application
+version: 0.1.0
+appVersion: "0.1.0"
+keywords:
+  - slides
+  - nginx
+  - reveal
+maintainers: []