* docs: add build instructions to README
Resolves#7
Added comprehensive build documentation covering:
- Prerequisites (CMake 3.25+, C++20 compiler)
- Building included examples
- Integrating Aurora into game decomp projects
- Available CMake options
Verified on macOS with clang by successfully building the simple example.
* qa: fix --recursive flag (no submodules) and add missing AURORA_CACHE_USE_ZSTD option
- Remove --recursive from clone command: repo uses FetchContent, not submodules
- Document AURORA_CACHE_USE_ZSTD option (default: ON) that was missing from the list
* move build instructions to docs/building.md