Add simple way to open pull request link in web or copy the URL to clipboard

### Feature summary

I can't find a simple way to open a pull request in the web or get the URL

### What problem are you trying to solve?

When asking to open a pull request, there's a link in the session chat I can click, but oftentimes I keep the session going for a long while until the PR is finally ready to be merged, but requires an approval from a peer. There's a nice pull request panel to the right hand side, and I've looked around it without finding something clickable to open the pull request in the web.

For the pull request in that screenshot, I just want to open or copy this link easily from the pull request panel: https://github.com/Devolutions/psign/pull/8

Maybe there's already a way to do it, but it's not obvious enough to me where it is, and I missed it

### Proposed solution

I'd like a simple, handy way of opening the PR in the web from that panel, and ideally, also a way copy the hyperlink to clipboard without opening it. This way, I can easily share the PR link in slack to get the approval needed from a colleague.

### Workflow impact

I have to waste a bit of time either opening the list of PRs from the web on the same project to find the right one, otherwise I'm sometimes lazy and ask in the session chat for the link, but it's a bit slow to wait for that.

### Installation context

_No response_

### Additional context

_No response_

Start in the desktop app's pull request panel and reproduce the workflow with the example PR link in the issue. Done means the panel provides an obvious way to open the pull request in the web and copy its URL without opening it.

Scritto dal modello di indicizzazione a partire dal testo della issue.