DO NOT MERGE: Add index to docker file

[bdraco]

Proposed change

Add index to docker file

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
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Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
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• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

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• Documentation added/updated for www.home-assistant.io

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To help with the load of incoming pull requests:

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[bdraco]

for testing only, remove this in favor of home-assistant/docker#297

[bdraco]

For these we can probably use --index-url

[frenck]

Closing this one, we have deployed at this point. Will rework this part later when 2023.10 has been shipped.

../Frenck