message: Add check for package.json:publishConfig.access to prepare script
diff: @@ -16,6 +16,13 @@ const normalize = name => name
  const name = normalize(pkg.name);
  +if (pkg.name.startsWith('@urql/')) {
  + invariant(
  + pkg.publishConfig.access === 'public',
  + 'package.json:publishConfig.access must be set to public for @urql/* packages'
  + );
  +}
  +
  invariant(
  path.normalize(cwd) !== path.normalize(workspaceRoot),
  'prepare-pkg must be run in a package.'
  