Expand description
Port of Luau::vformatAppend from Common/src/StringUtils.cpp.
Deviation (documented, behaviorally faithful): the C++ original is a
printf-style void vformatAppend(std::string& ret, const char* fmt, va_list args) built on vsnprintf. C va_list/varargs have no stable Rust
equivalent, and this crate targets stable + wasm32, so the formatting
mechanism is replaced by core::fmt: callers pass core::fmt::Arguments
(produced by format_args!) instead of a printf format string plus a
va_list. The observable effect — appending formatted text to a string — is
preserved; only the spelling of the format moves from %-specifiers to
Rust’s {} at the (eventually translated) call sites.