Add --json support to 'heroku builds'

[edmorley]

The output of heroku builds doesn't include all build attributes (for example the stack or buildpacks), and probably can't given the table of data shown is already pretty large.

Typically the way one can access additional data from the CLI is by using --json and then doing something with the response using jq.

However heroku builds --json fails with:

 ›   Error: Unexpected argument: --json
 ›   See more help with --help

As a workaround I have to instead install heroku-api-plugin and use:

h api /apps/<APP_NAME>/builds

...though that doesn't support passing custom range so fetches all builds rather than just the most recent N builds.

[drush]

+1