app/dcs/api/s3/s3-compatibility: update with the latest storj.io/gate…

…way/docs/s3-compatibility.md (#286)

This updates the page with the latest
storj.io/gateway/docs/s3-compatibility.md to make it the ground truth
and prepare for removal of storj.io/gateway/docs/s3-compatibility.md. It
also adds another context for GetBucketLocation from
#285, superseding this pull request.

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Co-authored-by: onionjake <[email protected]>
Co-authored-by: Michael Ferris <[email protected]>