Reimagine publish flow #2115

Right now when you hit publish you get redirected to /user-settings/extensions , this requires you to find the other publish button on that page that will finally open the publish popup ,

The problems I see with the current implementation are:

• The publish flow requires too many steps from the user
• Once you hit the popup you can only drag one extension at a time
• Given all the steps you already had to make, there's an additional publish button once you selected the extension you want to upload
• Once the extension it's being uploaded you don't get any feedback about if it's published blocked or whatever, you need to manually refresh the page to see that.

My proposal here would be:

• Create a separate publish page that already contains the drop-area first
• When the user hits the navbar publish button the next step will just be to drop or select the extension
• The extension should be published straight away, no need for further confirmation, it just adds friction (we can probably review that since extension versions cannot be re-uploaded)
• We should allow to publish multiple extensions at the same time, otherwise publishing through the webui gets really painful
• The UI should display state-changes of the just published extensions without requiring the user to constantly refresh the page.

I've created this PR trying to solve all the issues that I outlined above, any feedback is welcome #2098