Add WebUI dev documentation and skaffold fix.

[hacktobeer]

Description of the change

As the WebUI is build in Vue and we put a minified build in the API server it is not possible to debug this in the containers. This PR:

• adds a paragraph to the dev documentation on how to develop for the WebUI
• changes the skaffold config to prevent rebuilds of the api-server container when developing on the WebUI
• fixes the web README as npm run serve does not work as there is no serve profile.

Applicable issues

• fixes #

Additional information

Checklist

• [ ] All tests were successful.
• [ ] Unit tests added.
• [x] Documentation updated.