Create CODE_OF_CONDUCT.md

[louisa-seers]

As agreed in the TSC and as part of the charter, we've started to look at the code of conduct. I've asked the LF and this is the template they have given. Please feel free to let me know if there are any issues.

Related to Issue #20

[galasa-team]

Automatic triggering of the build is cancelled as user is not a member of the approved groups. Please ask an admin to review this PR and create a comment on the PR stating 'Approved for building'

[techcobweb]

The DCO check failed - you need to sign your commits, so we can be sure it's you changing the code. See https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits
So you need to do that whenever you git commit -m "message" -s -S