Provide documentation of multiple Element versions

[kfenner]

We deploy our release docs already to this s3 bucket: https://d2uqfzn4lxgtwv.cloudfront.net/

Now we want to make the following changes:

• Clean up s3 bucket
• Redirect element.siemens.io to the s3 bucket
• Point GitHub pages deployment (main branch) to dev.element.siemens.io (for example) and link that from the s3 bucket
• Document the whole thing