dns_option missing from compose schema

[ps-jay]

dns_option missing from the schema for compose

As discussed in docker/compose#5010 (comment), in order for Docker Compose to support an option provided by docker run, it needs to be added to the compose schema in this repository.

Could that be done, so that we may use the functionality to provide DNS options when using Docker Compose?

Steps to reproduce the issue:

1. Observe that dns and dns_search are in the schemas, but dns_option is not

Describe the results you received:
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Describe the results you expected:
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Additional information you deem important (e.g. issue happens only occasionally):
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Output of docker version:
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Output of docker info:
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Additional environment details (AWS, VirtualBox, physical, etc.):
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