C++26: Pack Indexing Simplifies Element Extraction

While C++11 introduced parameter packs, extracting specific elements remained cumbersome. C++26, thanks to proposal P2662R3, introduces pack indexing, allowing direct access to pack elements using the subscript operator, e.g., `T...[0]` for the first element. This leads to cleaner, more readable code and improved compile-time performance. Although negative indexing and slicing aren't yet supported, the feature is already highly usable, significantly improving C++ development.