Modernized, added new tests for Windows/Clang, macOS/AppleClang, and
MSYS.

New pattern for base docker images, and Windows now on a proper
running environment.

No longer included in base image.

A slight rework, instead of doing just the clang compiler, also uses
the symbolic frontend of gcc, just in case.

Errors now return a non-zero value, and errors are printed to std::cerr
instead of std::cout.

Now lists both the GitHub and GitLab locations.

Added Linux clang builds, and a clang-cl for Windows.

Performing platform tests and a compilation analysis stage.

The unicode version is now added to the end of the output file.

The unicode block size now defaults to a simple calculation function,
which can be substituted with the full enumerated set using the switches
as before.

Using items from the cmake-scripts repository.

version_str lines didn't have the semi-colon after it's definition, thus
causing the header to fail to be compilable.

So that others don't have to build and run the program themselves.

For all compilers.

Changed the default output to be .hpp instead of .h, and changed some
formatting of the generated file.

Now for refinement.

The ignore, license and clang-format files.