Release 1.3.0 (Beta)

What's Changed

• bump 3rd party dependencies to current versions
• optimise template load time (introduce ability to use boost::regex that is times faster than std::regex)

Fixed bugs

• small fixes across code base

Breaking change

• introduce new default ToJson filter implementation based on boost::json (rapidjson seems to become abandoned)
• get rid of git submodules in favour of CMake fetch_content

Full Changelog: 1.2.1...1.3.0-beta