Add an IDE-only workspace sample in the Dashboard getting started (without project)

Synced from eclipse/che issue

https://github.com/eclipse/che/issues/21554

Is your task related to a problem? Please describe

Currently from the UD, it is not possible to start an empty workspace. This story should target the following flow:

• As a user, I create an empty workspace from the dashboard UI
• Workspace is empty and I can clone any repository from the terminal
• Once the workspace is cloned I can generate a minimal devfile using the dedicated command e.g. "Generate Devfile"
• As I work on the project from the workspace I can update devfile accordingly, e.g. add extra commands and push it to the remote
• Once the changes are pushed I can share the repository with another user that would be able to replicate the same development environment

Describe the solution you'd like

There should be a dedicated "Blank / Empty / Scratch" devfile or a button "Start from scratch" / "Empty workspace" that would:

1. Create a workspace without any project based on the UDI image
2. Had the command for generating a minimal devfile v2 using the "Generate Devfile" command

Release Notes Text

A new example has been added in the Getting Started section of Eclipse Che Dashboard that allows users to start the IDE without any source code project. Git repositories can be opened from the IDE once the workspace is started.