Turn app manifest into a pluggable URL for the new app page

[ajhenry]

Is your feature request related to a problem?

No response

Describe the solution you'd like

Reading from the app manifest is tedious, there is an option to have the values prepopulated in the URL so when they visit the page the user does not need to select any permissions.

https://docs.github.com/en/apps/sharing-github-apps/registering-a-github-app-using-url-parameters

Describe alternatives you've considered

No response

Additional context

No response