[frontend] Tree view

[fcollonval]

Using @jupyter-notebook/react-components, display the results in a tree view:

        <TreeView>
          <TreeItem>
            File 1
            <TreeItem>
              Match 1
            </TreeItem>
            <TreeItem>Match 2</TreeItem>
            <TreeItem>Match 3</TreeItem>
          </TreeItem>
          <TreeItem>
            File 2
            <TreeItem>
              Match 1
            </TreeItem>
            <TreeItem>Match 2</TreeItem>
            <TreeItem>Match 3</TreeItem>
          </TreeItem>
          <TreeItem>
            File 3
            <TreeItem>
              Match 1
            </TreeItem>
          </TreeItem>
        </TreeView>

Task:

• Replace the pre tag with raw output with advanced tree view see example above
• Add theme connection script addJupyterLabThemeChangeListener to adapt component UX to JupyterLab theme; see https://github.com/madhur-tandon/jlab-image-editor/pull/3/files#diff-a2a171449d862fe29692ce031981047d7ab755ae7f84c707aef80701b3ea0c80R23