Some fixes, some new features.

• Implemented Link-Time Optimization (Ineffective on GCC) (link-time-optimization.cmake)
• Better code-coverage usability on Windows (code-coverage.cmake)
• Fixed code coverage ccov-all targets when using CMake pre-3.17 (code-coverage.cmake)
• Fixed code-coverage ccov-all targets on Windows (code-coverage.cmake)
• Added standard C++23 function (c++-standards.cmake)
• Added macros for C-standards from C90 to C23 (c-standards.cmake)
• New per-target export option (code-coverage.cmake)
• Remove double-running of code-coverage targets (code-coverage.cmake)
• Can now combine multiple sanitizers in one build (sanitizers.cmake)
• Add new Control Flow sanitizer optin (sanitizers.cmake)
• Add ability to make AFL++ (american fuzzy lop) fuzz instrumented builds (afl-fuzzing.cmake)

Changes from November 2020 -> January 2021

• Added new script that can build GLSL shader source files can be linked to a specified target and compiled for, complete with only re compiling only files modified since last compilation.
• Added files that allow for using the find_package function in CMake to find various libraries not included with CMake: fmt, assimp, glm, OpenXR and yaml-cpp.

Changes from April -> November 2020

• Changes primary branch from 'master' to 'main', including README links
• Fixed shared code not showing on ccov-all reports (with clang)
• Catch2 no longer uses 'master' as the default branch, as CMake tries to use. As such, the specific tag 'v2.x' is to be used, which safely follows Catch2's releases.

What it says on the tin.