[FEATURE] Move frontend code into a frontend folder of the main repo

[francostellari]

Problem or Use Case

I think it would be nice to move the frontend related code to its own frontend/ subfolder to match the backend.
It would make the repo more neatly organized.

Proposed Solution

Create a frontend/ subfolder and move the related code into it.
Adjust the scripts, docker files to match the new paths.

Are you willing to contribute?

• Yes, I'd like to help implement this feature.

Additional Context

No response

[rxinui]

/kind help wanted

[kubestellar-prow]

@rxinui: The label(s) kind/help, kind/wanted cannot be applied, because the repository doesn't have them.

In response to this:

/kind help wanted

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[MAVRICK-1]

I'm putting this PR on hold for now because there are a few frontend-related PRs that still need to be merged. Once those are completed, this can be reopened for resolution.