add option to enforce nil container marshaling as empty containers

[dedefer]

Description

PR for Issue #351

PR Was Proposed and Welcomed in Currently Open Issue

• This PR was proposed and welcomed by maintainer(s) in issue feature: Encode nil map/slice with cbor empty map/list tag #351
• Closes or Updates Issue feature: Encode nil map/slice with cbor empty map/list tag #351

Checklist (for code PR only, ignore for docs PR)

• Include unit tests that cover the new code
• Pass all unit tests
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[fxamacker]

Thanks for this contribution, it passed fuzz tests!

There some very minor nits (naming convention) which I can address after merge.

Thanks again for your patience and nice work!

[fxamacker]

I made some changes in a follow up PR #377, mostly to rename the options.

p.s. My schedule is unpredictable this week and I saw that you've been inactive on GitHub for a few months, so I went ahead instead of requesting changes in PR review. I hope you don't mind.

[dedefer]

Thank you very much! And alao thanks for naming changes!