fix: CMEK key-creation instructions in CONTRIBUTING.md missing some steps (#4356)
fix: CMEK key-creation instructions in CONTRIBUTING.md missing some steps (#4356)

* fix: Key-setup fixes

* inclue a reference link

* fixed shell punctuation, spelling and consistency.

Co-authored-by: Christopher Wilcox <1a61e7a0041d068722f1c352424109b22f854ce0@google.com>
googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go