[Python] Add section on samples in templated CONTRIBUTING.rst

[parthea]

python-compute has a section on Samples and code snippets in CONTRIBUTING.rst. This could be added to the templated CONTRIBUTING.rst doc here so it can be used in all repos.

[parthea]

@busunkim96 @leahecole #1159 was merged this morning. I understand there are some tweaks needed as the code snippet may not work on all repos. I'm going to keep this issue open to track the fix.

[leahecole]

Given the monorepo migration, I think we can close this @parthea, but if you think it should be reopened please do so and add any additional context about its progress/relevance!