Allow to open PR on web from PR view when showing multiple

[bpasero]

Here I really miss a way to click on the 🌐 icon to open the PR externally:

[alexr00]

@bpasero you just want to open github.com to the PR? I can add an action for this.

[bpasero]

Yeah like this one:

[Santhoshmani1]

Hey there. I would like to contribute to this project and this issue would be a good starting point.

I have build the extension locally. For opening the pr on github, we can modify the menus -> view/item/context to use the existing pr.openPullRequestOnGithub command in package.json file.

I am happy to send a pull request with the required changes.