De-dockerize landing page

[worldthumbler]

Is your feature request related to a problem? Please describe. Building the docker container is always linked to extra time for testing and deploying. In our case the modification of the docker-container is mainly due to changes on the landing page (and a few in the language file).

Describe the solution you'd like Addition of a possible override for the landing page to reduce the cases where a customization of the greenlight container is necessary.

Describe alternatives you've considered Other options to allow any kind of (semi-)automated customization methods are considered insecure. e.g. build the container customized when file xy is present or the corresponding value is set in the config file. Setting them would trigger the container to (re)build at every startup. To prevent that more controls like checking the files for change and determining the necessity to rebuild the container would be needed.

Additional context A Fallback solution should be implemented in cases where the override files cause in error in starting the container.

The development of the feature is clearly dependent on the potential benefit and the effort required. Clearly the cases it would be used must be sufficient high.