Create devcontainer.json

[longjason529]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
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• Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> ☕️

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[google-cla]

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