[documentation] Transient dependency sentencepiece requires cmake to install correctly.

[CalebCourier]

sentencepiece, a dependency of unbabel-comet requires cmake when building its wheel. Since many environments do not include cmake by default, it would be useful to add a note to this validator's README to mention this requirement.

On Linux and MacOS this information can be gleaned from the error show, but the Windows error is not as transparent to the root cause of the installation failure. See this issue for an example of the Windows error: guardrails-ai/guardrails#1167

[CalebCourier]

Update on this behaviour:

In addition to cmake, when installing sentencepiece<0.2.x (a transient dependency of this validator), it also requires other C++ build tools such as g++. This is noted in their README here: https://github.com/google/sentencepiece?tab=readme-ov-file#build-and-install-sentencepiece-command-line-tools-from-c-source

It also appears that this is only needed in versions of python 3.12 and above since there are wheels published for the versions below this and thus the wheel does not need to be built on the client machine.