Fix line wrapping inside JSX tags assigned to variables

[ony3000]

This PR closes #104.

// Input
function Foo() {
  let elem = (
    <div className="lorem ipsum dolor sit amet consectetur adipiscing elit proin ex massa hendrerit eu posuere eu volutpat id neque pellentesque">
      content
    </div>
  );
  elem = (
    <div className="lorem ipsum dolor sit amet consectetur adipiscing elit proin ex massa hendrerit eu posuere eu volutpat id neque pellentesque">
      content
    </div>
  );
  return elem;
}

// prettier-plugin-classnames 0.8.0
function Foo() {
  let elem = (
    <div
      className="lorem ipsum dolor sit amet consectetur adipiscing elit proin ex
        massa hendrerit eu posuere eu volutpat id neque pellentesque"
    >
      content
    </div>
  );
  elem = (
    <div className="lorem ipsum dolor sit amet consectetur adipiscing elit proin ex massa hendrerit eu posuere eu volutpat id neque pellentesque">
      content
    </div>
  );
  return elem;
}

// prettier-plugin-classnames 0.8.1
function Foo() {
  let elem = (
    <div
      className="lorem ipsum dolor sit amet consectetur adipiscing elit proin ex
        massa hendrerit eu posuere eu volutpat id neque pellentesque"
    >
      content
    </div>
  );
  elem = (
    <div
      className="lorem ipsum dolor sit amet consectetur adipiscing elit proin ex
        massa hendrerit eu posuere eu volutpat id neque pellentesque"
    >
      content
    </div>
  );
  return elem;
}