src/language-markdown/parser-markdown.js/mergeContinuousTexts
function mergeContinuousTexts() {
  return ast =>
    map(ast, node => {
      if (!node.children) {
        return node;
      }
      const children = node.children.reduce((current, child) => {
        const lastChild = current[current.length - 1];
        if (lastChild && lastChild.type === "text" && child.type === "text") {
          current.splice(-1, 1, {
            type: "text",
            value: lastChild.value + child.value,
            position: {
              start: lastChild.position.start,
              end: child.position.end
            }
          });
        } else {
          current.push(child);
        }
        return current;
      }, []);
      return Object.assign({}, node, { children });
    });
}