code: function extractUsernameFromLink(steemitLink) {
    if (isValidSteemitLink(steemitLink)) {
      const usernamePos = steemitLink.search(/\/@.+\//);
      if (usernamePos === -1) return;
  
      const firstPart = steemitLink.slice(usernamePos + 2); // adding 2 to remove "/@"
      return firstPart.slice(0, firstPart.search('/'));
    }
  }
docs: Should input a full steemit article link and return the username of the author
  @param {string} steemitLink