Adding linear ticket requirement to PRs#31

TechnoFinch wants to merge 2 commits intomaintogethercomputer/together-go:mainfrom

mark/eng-1894-enforce-that-github-prs-link-to-an-issue-in-lineartogethercomputer/together-go:mark/eng-1894-enforce-that-github-prs-link-to-an-issue-in-linearCopy head branch name to clipboard