code: function getPercentage() {
    const type = NodeType.PercentageType;
    const token = tokens[pos];
    const line = token.ln;
    const column = token.col;
    const content = getNumberOrInterpolation();
    const end = getLastPosition(content, line, column, 1);
  
    // Skip `%`.
    pos++;
  
    return newNode(type, content, line, column, end);
  }
docs: Get a percentage node that contains either a number or an interpolation
  @return {Object} The percentage node