Provide a specific example of creating a MigStorage from API with a S3 bucket using a specific region.

[jwmatthews]

Refer to slack conversation

A user was trying to use Crane from API and ran into some difficulty in learning how to configure a MigStorage with a S3 repo that used a non us-east-1 region. The configuration parameter wasn't apparent, it took me a few minutes of hunting to see we documented 'awsRegion' in a comment here:
https://github.com/konveyor/mig-operator/blob/master/docs/usage/MTCAPIDoc.md#migstorages

Feels like our docs on API migrations would benefit from some attention and cleanup.
I think we have pieces spread around, but don't feel we have a solid API guide we can point someone to for an easy on-ramp.