function isDevSiteHTMLPage(filename, contents) {
  // const RE_HTML_TAG = /<html.*?>/;
  const RE_HTML_DEVSITE = /<html\s.*?devsite.*?>/;
  return RE_HTML_DEVSITE.test(contents);
}
Checks if a file is a DevSite HTML page.

@param {string} filename The WebFundamentals file path.
@param {string} contents The contents of the file
@return {Boolean} True if it is, false if not.