The template literal that's returned by the following function isn't being transpiled during the distribution build process:
Source file (/src/index.js):
const getIndent = level => `${eol}${indentString.repeat(level)}`;
So when I import posthtml-beautify into my project, /lib/index.js still contains a template literal:
getIndent = function (level) { return `${eol}${indentString.repeat(level)}` }
This breaks my app in IE11 because template literals are not supported by that browser.