feat: add Samples section to CONTRIBUTING.rst (#229)

Source-Link: https://github.com/googleapis/synthtool/commit/52e4e46eff2a0b70e3ff5506a02929d089d077d4
Post-Processor: gcr.io/repo-automation-bots/owlbot-python:latest@sha256:6186535cbdbf6b9fe61f00294929221d060634dae4a0795c1cefdbc995b2d605
2 files changed