Prevent squash and merge for new repos

[alexanderleegs]

Some repos have encountered issues because agency users mistakenly used squash and merge to merge changes on their staging branch to master - this could potentially cause merge conflicts because squash and merge creates an entirely new commit instead of preserving the existing commits, so a squashed commit is treated as different from what already exists on staging. To rectify this, we should ban squash and merge for new repos, since new repos should be using the cms and have no need for branches off staging.

We can do this by adding
allow_squash_merge: true
as a parameter to the create request:

octokit.repos.createInOrg({
      org: 'isomerpages',
      name: repoName,
      description: `Staging: https://${repoName}-staging.netlify.app | Production: https://${repoName}-prod.netlify.app`,
      private: false,
    }),