Provide an affordance for opening HTML files directly in a web browser

[jmcphers]

Today, if you have an HTML file open, there is no way to open it in a web browser with one click. You need to first open it in Positron's Viewer pane; from there you can open it in your system's web browser.

These gestures both open an HTML file in the Viewer pane:

Once it's open in the Viewer pane, you can do this:

But that's two clicks and it is not obvious that it's the route to seeing your file in a browser.

Proposal:

• Add an "Open in Browser" to the context menu in the Explorer view for HTML files
• Add an "Open in Browser" action to the Editor Actions bar for HTML files