README: Fix SVG diagrams not rendered properly in tab (#292)

When clicking on diagrams on GitHub they should be displayed in large.
However, on click the file is opened (still small).
When clicking on "Raw" the file opens full screen but is not rendered
properly.
Example:
https://raw.githubusercontent.com/cloudogu/gitops-playground/refs/heads/main/docs/gitops-playground-features.drawio.svg

Cause is Content-Security-Policy (CSP) used by raw.githubusercontent.com
:
img-src is limited, and data: URIs are not allowed.

To work around this, we could save the images as PNG.
PNG needs more size and is binary.
This would bloat our repo and slow down the loading time of our main
README.

Alternative: Add links that render the file via jsdeliver.
Disadvantage: Depending on a remote service.
It is only necessary for a quick full-screen view, though.
So, this solution seems pragmatic.

Minor fixes:

- Set height="100%" to SVG diagrams so opening them in full screen
scales them down to match the wide screen.
- Make clear the visualization tool is grafana
- Fix copyright background

Author: schnatterer

README.md

@@ -18,7 +18,7 @@ Kubernetes clusters:
 The gitops-playground is derived from our experiences in [consulting](https://platform.cloudogu.com/consulting/kubernetes-und-gitops/?mtm_campaign=gitops-playground&mtm_kwd=consulting&mtm_source=github&mtm_medium=link),
 operating our internal developer platform (IDP) at [Cloudogu](https://cloudogu.com/?mtm_campaign=gitops-playground&mtm_kwd=cloudogu&mtm_source=github&mtm_medium=link) and is used in our [GitOps trainings](https://platform.cloudogu.com/en/trainings/gitops-continuous-operations/?mtm_campaign=gitops-playground&mtm_kwd=training&mtm_source=github&mtm_medium=link).  
 
-![Playground features](docs/gitops-playground-features.drawio.svg)
+[![Playground features](docs/gitops-playground-features.drawio.svg)](https://cdn.jsdelivr.net/gh/cloudogu/gitops-playground@main/docs/gitops-playground-features.drawio.svg "View full size")
 
 ## TL;DR
 
@@ -137,9 +137,9 @@ scenario with the Cloudogu EcoSystem (CES). Here better security and build perfo
 Jenkins build agents spawned in the cloud.
 
 ### Overview
-| Playground on local machine                                             | Production environment with Cloudogu EcoSystem                                                                                                                                                        |
-|-------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| ![Playground on local machine](docs/gitops-playground-local.drawio.svg) | ![A possible production environment](docs/gitops-playground-production.drawio.svg) |
+| Playground on local machine                                                | Production environment with Cloudogu EcoSystem                                       |
+|----------------------------------------------------------------------------|--------------------------------------------------------------------------------------|
+| [![Playground on local machine](docs/gitops-playground-local.drawio.svg)](https://cdn.jsdelivr.net/gh/cloudogu/gitops-playground@main/docs/gitops-playground-local.drawio.svg "View full size") | [![A possible production environment](docs/gitops-playground-production.drawio.svg)](https://cdn.jsdelivr.net/gh/cloudogu/gitops-playground@main/docs/gitops-playground-production.drawio.svg "View full size") |
 
 ### Create Cluster
 
@@ -733,7 +733,7 @@ When installing the GitOps playground, the following steps are performed to boot
 
 From there, everything is managed via GitOps. This diagram shows how it works.
 
-![](docs/argocd-repos.svg)
+[![](docs/argocd-repos.svg)](https://cdn.jsdelivr.net/gh/cloudogu/gitops-playground@main/docs/argocd-repos.svg "View full size")
 
 1. The `bootstrap` application manages the folder `applications`, which also contains `bootstrap` itself.  
    With this, changes to the `bootstrap` application can be done via GitOps. The `bootstrap` application also deploys
@@ -793,7 +793,7 @@ The short answer is: As of 2023-05, version 0.4.15 it looks far from ready for p
 
 Here is a diagram that shows how the repo structure created by autopilot looks like:
 
-![](docs/autopilot-repo.svg)
+[![](docs/autopilot-repo.svg)](https://cdn.jsdelivr.net/gh/cloudogu/gitops-playground@main/docs/autopilot-repo.svg "View full size")
 
 Here are some thoughts why we deem it not a good fit for production:
 
@@ -979,7 +979,7 @@ The applications implement a simple staging mechanism:
 * For some applications working without CI Server and committing directly to the GitOps repo is pragmatic  
   (e.g. 3rd-party-application like NGINX, like [`argocd/nginx-helm-umbrella`](argocd/example-apps/argocd/nginx-helm-umbrella.ftl.yaml))
 
-![app-repo-vs-gitops-repo](docs/app-repo-vs-gitops-repo.svg)
+[![app-repo-vs-gitops-repo](docs/app-repo-vs-gitops-repo.svg)](https://cdn.jsdelivr.net/gh/cloudogu/gitops-playground@main/docs/app-repo-vs-gitops-repo.svg "View full size")
 
 Note that the GitOps-related logic is implemented in the
 [gitops-build-lib](https://github.com/cloudogu/gitops-build-lib) for Jenkins. See the README there for more options like