Warn about quotes interpretation in README instructions for using API docker image directly

[alyssadai]

In the below sections of the README, we should explicitly instruct users to not wrap any space-separated values for variables in the .env file in quotation marks:

• https://github.com/neurobagel/api#option-2-use-the-latest-image-from-docker-hub
• https://github.com/neurobagel/api#option-3-build-the-image-using-the-dockerfile
  (for now, it's probably just the NB_API_ALLOWED_ORIGINS variable that this applies to)

See our internal wiki https://github.com/neurobagel/documentation/wiki/Docker#docker-cli-docker-run for why the quotes are a problem

Originally posted by @surchs in neurobagel/federation-api#22 (review)

[github-actions]

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[samadpls]

Hi @alyssadai, I have created a PR #284 related to this ticket. Could you please review it when it's convenient for you?
Thanks so much!

[surchs]

🚀 Issue was released in v0.2.0 🚀