title: WebExtensions API - create a "popup" with no title bar title and buttons
body: <p>I would like to know if there is a way to create the same kind of a popup window that you can get with the API for toolbar button or address bar button described here: <a href="https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/user_interface/Popups" rel="nofollow noreferrer">Popups API documentation</a> Either achieved true the WebExtensions API or other means.</p>
  <p>More specifically I do not need the window title bar or title bar buttons nor the address bar, forward/backward buttons etc. Like shown here:</p>
  <p><a href="https://i.stack.imgur.com/B8sss.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/B8sss.png" alt="Pop up example picture" /></a></p>
  <p>According to the documentation you can create extension pages, but they do include title bar and title bar buttons - <a href="https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/user_interface/Extension_pages" rel="nofollow noreferrer">Extension pages API documentation</a>
  Like this one: <a href="https://i.stack.imgur.com/UVABo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UVABo.png" alt="enter image description here" /></a></p>
  <p><strong>Purpose:</strong> I have created my self an extension which adds a button to the contents of a specific web site. When the button is pressed it opens a new tab with a certain cross origin web page. I do not want to click around closing the opened new tab to go back to the previous. A pop up page here will make my life a bit easier as whenever you click outside of it - it closes.</p>
  <p><strong>What I tried:</strong> Tried opening the external web page as a modal <code>&lt;iframe&gt;</code>. But this leads to a CSP violation in the rare cases that I need to interact with it.</p>
  <p><em>The used images are from the MDB web docs</em></p>