Update SPIRV-Cross to latest

Update catch2 version to latest

Update init.sh to include installing Catch2 libraries so that cmake doesnt fail when first syncing the project

Update GLFW version to latest

Update some old comment formats

Define NOMINMAX before Windows.h

Merge pull request #176 from flingengine/remove-null-checks

Remove unnecessary null checks when deleting issue #174

Added CLion build files to ignore

Update SPIRV-Cross module, and clean up a few C++20 warnings that popped up. Compiled successfully with clang++

spdlog v1.3.1

set C++ version to 20

Update to latest catch 2 stuff, and remove the now unused vulkan_sdk_headers.h file to get building

Update catch2 to release tag v3.5.3

Submit fix for linux compile, update appveyor to hopefully fix SDK install