Update Dockerfile for packaging in custom integrations

[mfw78]

Problem When package distributors (such as a dappnode package) want to provide an integration for the bee-dashboard when distributing the bee package, it is a huge help to be able to setup the environment for the user without their intervention.

This includes:

• API endpoints (Debug and normal) for bee
• RPC endpoints (it's important to note here that the environment in which a docker image may run, may very well differ to that of the bee node that's running, and therefore using an RPC provider returned from bee may not fit all use cases, unless all chain interaction was completely abstracted away into the bee node.

Solution To assist package developers, it would be beneficial for Swarm to provide pre-built docker containers in line with the release cycle, with version tags, and latest tag (and in doing so, provide builds for both linux-amd64 and linux-arm64. This will significantly reduce cross-compilation time for the arm64 target for integrators (effectively eliminating it as such) and provide a "reference" implementation from which to integrators can start from.

In doing so, it would be very handy to be able to specify API URLs and RPC URLs via environment variables passed to the docker container at runtime.