Get total size of all buckets with aws s3 ls --summarize

[tim-finnigan]

Is your feature request related to a problem? Please describe.
Currently when running aws s3 ls --summarize it returns:

[s3-bucket-1]
[s3-bucket-2]
...

Total Objects: 0
   Total Size: 0

Describe the solution you'd like
aws s3 ls --summarize to return the Total Objects and Total Size of all buckets:

[s3-bucket-1] (Total Objects: N | Total Size: N)
[s3-bucket-2] (Total Objects: N | Total Size: N)
...

Total Objects: [Combined Objects]
   Total Size: [Combined Size]

Describe alternatives you've considered
A workaround script could loop through each bucket and parse this info with a command like this:
aws s3 ls my-bucket-name --summarize --recursive --human-readable | tail -2

(^This would be easier if there were a --summary-only option as requested here: #2250)

[Yoshiitaka]

@tim-finnigan May I try to handle to this Issue? :)

[tim-finnigan]

@Yoshiitaka sure! Thanks for offering to work on it. We recently made updates to our contribution process here that could be helpful to review as well.