Add a setting to hide the top bar programmatically

[venpopov]

As far as I can tell there is no way to set the visibility of positron's custom top bar to hidden by default. I don't find it useful and it just takes vertical space. You can hide it manually, but I would like to be able to specify it to be hidden in my settings.json file. All other standard vscode bars can be disabled via the workbench setting namespace. E.g.:

"workbench.activityBar.location": "hidden",
"workbench.statusBar.visible": false,
"workbench.editor.showTabs": "none",

Please add a setting to hide the top bar as well.

[petetronic]

Thank you for the feedback, sending to Triage for review.