20240806; version 2.109:
  * Now operator=() supports the boolean values, true and false.
  * Modified operator=() so that a descendant or ancestor of *this can
    be copied to *this, such as:
      js["a"]("b")("c") = js["a"];
      js["a"] = js["a"]["b"]["c"];

20240804; version 2.108:
  * Added an overload function to num() whose return type can be
    specified by the template argument.
  * Fixed a bug that caused a compilation error since version 2.106 when
    assignment of a string is done with operator=().
  * Fixed a bug that caused a compilation error since version 2.107 when
    type() is called.

20240804; version 2.107:
  * Improved the performance of parsing.

20240802; version 2.106:
  * Improved the performance of stringify() and to_string().
  * Added an overload function to stringify() and to_string() whose
    return type can be specified by the template argument.
  * Modified so that parsing and stringifying can be done with a string
    type different from the string type of the ctl::json classes.
  * Added new types, wjson, u16json, which handle a string as UTF-16.

20240730; version 2.105:
  * Fixed a problem of u8json that caused a compilation error.
  * Moved the base class into an internal namespace.

20240728; version 2.104:
  * Reduced memory usage.

20240727; version 2.103:
  * Improved the parser to avoid unnecessary copying of data.
  * Restricted the unescaping operation to being performed in parse()
    only.
  * Changed the name of the member function raw() to set_str().

20240721; version 2.102:
  * Fixed so that escape sequences would not be interpreted when
    outputting a JSON.

20240720; version 2.101:
  * Added the include guard that was accidentally missing.

20240616; version 2.100:
  * The first released version.