docs: fix resize and swap examples in README

[Lxc097]

The README API table shows two-argument calls to cvector_resize and cvector_swap, but both macros require three arguments. Copying either call currently produces a macro argument-count error.

Update the resize comparison to v.resize(count, value) / cvector_resize(v, count, value), and use cvector_swap(v, other, int) for the table's integer vectors. Briefly explain the fill-value and element-type arguments.

Validation on Windows with MinGW-w64 GCC 16.2.0:

• Reproduced the argument-count errors by compiling the calls extracted from the original README.
• Compiled the corrected calls with -std=c89 -pedantic-errors -Wall -Wextra -Werror and ran assertions for initialization and swapping.
• Built and ran the existing unit-tests.c (18 tests passed) and test.c using -std=gnu90 -Wall -Wextra -Werror.
• git diff --check passed.

CMake/CTest was not run: the local CMake executable exits with Windows status 0xC0000135. The existing test programs were compiled and run directly with GCC.