Suggestion: Show size of packages

[Areahints]

Expected behavior

Expect to see download size of the package.

useful when on a metered connection.

[evandandrea]

While the initial download size would be straightforward to present, it would be misleading if that's also interpreted as how much will be downloaded on update.

Snap updates are downloaded as deltas from the version currently installed. As many different revisions of any app will be installed, this size is impossible to know.

[matthewpaulthomas]

I don’t think updates being smaller is a reason to omit the initial size. Other web storefronts show it regardless.

[Areahints]

Information of the package and its size is always relevant, even if you don't want to display this information on the site, when the install command is run on the terminal, we should get information about how much data is about to be downloaded, it's useful for cases of bandwidth and storage.