Include GitHub Pull Requests Extension

[petetronic]

We should consider including the GitHub Pull Requests extension by default, at least for desktop. Many users will collaborate with teams using GitHub as the source control system for their projects, and this extension also adds an Accounts menu option to sign in and out of your GitHub account in Positron.

[testlabauto]

Verified Fixed

Positron Version(s) : 2025.06.0-124
OS Version          : OSX

Test scenario(s)

Completely stop Positron
rm ~/.positron/extensions/.version
Restart Positron
Extension is present

Link(s) to TestRail test cases run or created: