code: public static String removeStart(final String str, final String removeStr) {
          if (N.isNullOrEmpty(str) || N.isNullOrEmpty(removeStr)) {
              return str;
          }
  
          if (str.startsWith(removeStr)) {
              return str.substring(removeStr.length());
          }
  
          return str;
      }
docs: <p>
  Removes a substring only if it is at the beginning of a source string,
  otherwise returns the source string.
  </p>
  
  <p>
  A {@code null} source string will return {@code null}. An empty ("")
  source string will return the empty string. A {@code null} search string
  will return the source string.
  </p>
  
  <pre>
  N.removeStart(null, *)      = null
  N.removeStart("", *)        = ""
  N.removeStart(*, null)      = *
  N.removeStart("www.domain.com", "www.")   = "domain.com"
  N.removeStart("domain.com", "www.")       = "domain.com"
  N.removeStart("www.domain.com", "domain") = "www.domain.com"
  N.removeStart("abc", "")    = "abc"
  </pre>
  
  @param str
  the source String to search, may be null
  @param removeStr
  the String to search for and remove, may be null
  @return the substring with the string removed if found, {@code null} if
  null String input
  @since 2.1