fixes #58

Problem

When a user selects "Set As Workspace Environment" for an environment that's already selected as the workspace environment, there's no feedback provided to the user. This can be confusing, as it appears that nothing happens when clicking the button.

Solution

This PR adds feedback to users when they attempt to select an environment that's already set as the workspace environment:

1. When a user has one folder/project open and tries to set the same environment that's already selected
2. The user will now see an information message: "This environment is already selected for the workspace." but its more verbose

Fixes #58 and refined by @eleanorjboyd