When Theia first loads, open index.html in editor pane

When the user first lands in his or her instance of Theia, I’d like to discern if there is an index.html file in the root of the directory, and if so, open it immediately in an editor pane. The editor pane should open in the left side of the screen, right next to the file browser.

So far, I have this:

    async onStart(app: FrontendApplication) {

      // If an index.html is in the root dir, open it in an editor pane.
      this.workspaceService.onWorkspaceChanged(foo => {
        // What should I do here?

@briandant is the topic not already covered by the previous post: By default, open html file in preview.

Thanks for checking!

My question there was not asked properly, so the answer only got me part of the way there. (In that other question, we answered "how can I open a preview when an .html file is opened by the user. In this newer question, I want to ask "how can I open an index.html in an editor pane as soon as Theia loads in the browser.) Which is why I thought I should ask a better question in this thread.

Can you tell me how to do this? a) search for an index.html when Theia first loads and then b) open that index.html in an editor pane. (And yes, when this index.html opens in an editor on the left, I still want the preview to open on the right.)