fix(core/workflow-steps): onStepSelected event

[goncalosard]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (yarn build) was run locally and any changes were pushed
• Unit tests (yarn test) were run locally and passed
• Visual Regression Tests (yarn visual-regression) were run locally and passed
• Linting (npm lint) was run locally and passed

Pull request type

Please check the type of change your PR introduces:

• Bug fix
• Feature
• Refactoring (no functional changes, no API changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

[IX-314]

What is the new behavior?

• Now onStepSelected works correctly emiting the index of the selected step.

Does this introduce a breaking change?

• Yes
• No

[nuke-ellington]

Unit test case missing

[danielleroux]

Fix not working:

        <ix-workflow-steps
          onStepSelected={(event) => {
            console.log(event.detail);
          }}
        >
          <ix-workflow-step>Step 0</ix-workflow-step>
          <ix-workflow-step>Step 1</ix-workflow-step>
          <ix-workflow-step>Step 2</ix-workflow-step>
        </ix-workflow-steps>

Should print the index of the step.

[nuke-ellington]

Small change - lgtm otherwise

[nuke-ellington]

lgtm