README.md fix for git submodule sync & --version / --help

[jamylak]

• README.md fix for git submodule sync
• --version
• --help

[Copilot]

Pull request overview

This PR adds command-line help and version flags to the vsdf tool, and improves the documentation by adding git submodule initialization instructions to all build sections.

Changes:

• Added --help and --version command-line flags to src/main.cpp
• Added git submodule update --init --recursive commands to all build and test sections in README.md
• Added a new "Populate submodules" section as step 0 in QUICKSTART.md

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/main.cpp	Adds --help and --version flags with supporting functions, and includes spdlog/fmt/fmt.h for formatted output
README.md	Adds git submodule initialization command before all cmake build commands (4 locations: Linux/macOS build, Windows build, Linux/macOS test build, Windows test build)
QUICKSTART.md	Adds a dedicated "0) Populate submodules" section with the git submodule command at the beginning of the quickstart guide

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[Copilot]

The printHelp function only shows a basic usage example with the --toy option, but doesn't document other available flags like --headless, --frames, --log-level, --debug-dump-ppm, or the FFmpeg-related options that are listed in the README. Consider expanding the help text to include all available command-line options, or at least the most commonly used ones, to make the tool more discoverable for users.

Suggested change

	fmt::print("Usage: {} [options] <shader.frag>\nExample: {} --toy "
	"shaders/testtoyshader.frag\n",
	exe, exe);
	fmt::print(
	"Usage: {} [options] <shader.frag>\n"
	"\n"
	"Options:\n"
	" --toy Use Shadertoy-style template for the fragment shader\n"
	" --headless Run without creating a window (offscreen rendering)\n"
	" --frames <N> Limit the number of frames to render before exiting\n"
	" --log-level <LEVEL> Set log verbosity (trace, debug, info, warn, error, critical, off)\n"
	" --debug-dump-ppm <DIR> Dump rendered frames as PPM files into directory DIR\n"
	#if defined(VSDF_ENABLE_FFMPEG)
	" [FFmpeg] Additional FFmpeg encoding options are available; see README\n"
	#endif
	"\n"
	"Example:\n"
	" {} --toy shaders/testtoyshader.frag\n",
	exe, exe);