🐛 Bug Report

Lib version: 3.8.2

Steps To Reproduce

1. In IE11

require('regenerator/runtime');
const Excel = require('exceljs/dist/es5/exceljs.bare');

2. Open the page that uses exceljs in IE11

The expected behaviour:

exceljs should work fine in IE11

Possible solution (optional, but very helpful):

The root cause is that exceljs uses saxes that uses xmlchars.
And xmlchars uses regular expressions with the unicode flag ("u") that cannot work in IE (so an error "Invalid range in character set" is thrown)

new RegExp("^["+t.NAME_START_CHAR+"]$","u")