[Enhancement] Update button on detail view of package

[DeanmvSG]

Replicate the "Update" button in the Available Updates view that is on the list of each package, to also be in the detail view of that package.

Current and suggested behavior

I often find myself seeing that there is packages to update in the "Updates" page. Then click into the package to read the changelog/description of that package and then from in there, there is no update button. You then have to go back to the "Updates" view to actually update the package.

Why would the enhancement be useful to most users

If you're like me it saves you one whole click (😱) so that you don't have to go back to the list of available updates.

Screenshot

Atom Version: 1.90-beta0 OS and Version: macOS Sierra (10.12 beta 2)