Expose both shared and static libraries as separate CMake imported
targets (ghostty-vt and ghostty-vt-static) rather than toggling
between them with BUILD_SHARED_LIBS. The zig build already produces
both in a single invocation, so both are always available.
The find_package config template is updated to export both targets
as ghostty-vt::ghostty-vt and ghostty-vt::ghostty-vt-static.
Add a c-vt-cmake-static example that demonstrates linking the static
library via FetchContent with -Dsimd=false to avoid C++ runtime
dependencies.
