static findPathInImportDeclaration(ast, name) {
    let path = null;

    babelTraverse(ast, {
      noScope: true,
      enter: function(_path) {
        const node = _path.node;
        if (node.type !== 'ImportDeclaration') return;

        for (const spec of node.specifiers) {
          const localName = spec.local.name;
          if (localName === name) {
            path = node.source.value;
            _path.stop();
          }
        }
      }
    });

    return path;
  }
find file path in import declaration by name.
e.g. can find ``./foo/bar.js`` from ``import Bar from './foo/bar.js'`` by ``Bar``.
@param {AST} ast - target AST.
@param {string} name - identifier name.
@returns {string|null} file path.