backSpaceHtmlChars(curString, curStrPos, self) {
    if (self.contentType !== 'html') return curStrPos;
    const curChar = curString.substring(curStrPos).charAt(0);
    if (curChar === '>' || curChar === ';') {
      let endTag = '';
      if (curChar === '>') {
        endTag = '<';
      } else {
        endTag = '&';
      }
      while (curString.substring(curStrPos - 1).charAt(0) !== endTag) {
        curStrPos--;
        if (curStrPos < 0) {
          break;
        }
      }
      curStrPos--;
    }
    return curStrPos;
  }
Backspace HTML tags and HTML Characters
@param {string} curString Current string
@param {number} curStrPos Position in current string
@param {Typed} self instance of Typed
@returns {number} a new string position
@private