What is this new syntax gql`string`

It's called a tagged template. Template literals (`...`) can be prefixed with a function name. Upon evaluation, this function will be called and the static and dynamic parts of the template literal are passed to the function. Example:

function foo(staticParts, dynamicParts) {
  console.log(staticParts, dynamicParts);
}

foo`this is a ${42} test`

Tagged templates can be used to create domain specific languages, such as in this example.

There are many questions around tagged templates you can learn more from.

It's called a template literal.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals

Not only does it allow you to do multi-line formatting like your example above, but it also makes it easier to mix expressions in with string content.