Add support for other hardware platforms

[jsf9k]

💡 Summary

Add support for other hardware platforms to this Docker image.

Motivation and context

This will allow us to use AWS Graviton, for instance.

Implementation notes

Note that this is not yet possible as there is not yet a multi-platform Docker image available for cisagov/pshtt.

[NeckBeardPrince]

Yes, please. Using a M2 Macbook and using buildx --platform linux/arm64/v8.

#0 3.311 INFO: pip is looking at multiple versions of docopt to determine which version is compatible with other requirements. This could take a while.
#0 3.312 INFO: pip is looking at multiple versions of <Python from Requires-Python> to determine which version is compatible with other requirements. This could take a while.
#0 3.312 INFO: pip is looking at multiple versions of pshtt to determine which version is compatible with other requirements. This could take a while.
#0 3.313 ERROR: Cannot install pshtt because these package versions have conflicting dependencies.
#0 3.313
#0 3.313 The conflict is caused by:
#0 3.313     sslyze 2.1.4 depends on nassl<2.3.0 and >=2.2.0
#0 3.313     sslyze 2.1.3 depends on nassl<2.3.0 and >=2.2.0
#0 3.313
#0 3.313 To fix this you could try to:
#0 3.313 1. loosen the range of package versions you've specified
#0 3.313 2. remove package versions to allow pip attempt to solve the dependency conflict
#0 3.313
#0 3.313 ERROR: ResolutionImpossible: for help visit https://pip.pypa.io/en/latest/topics/dependency-resolution/#dealing-with-dependency-conflicts
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Dockerfile-x:70
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  68 |     # isn't required here.)
  69 |     ###
  70 | >>> RUN pip install --no-cache-dir --upgrade pshtt==0.6.10
  71 |
  72 |     ###
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