Document mwrap module wrappers and runnable package templates #835

Existing C and C++ libraries are being published as module wrappers under mcpplibs.mwrap. The usage guidance should distinguish package/module names from the original API namespaces, explain additive feature selection, and show the package-owned mcpp new --template workflow.

Update the usage skill and matching English/Chinese documentation, linking the maintained index specification rather than duplicating its packaging rules. Verify every command and the qualified self.name template placeholder against the current implementation.

This is part of the OpenCV 5.0.0 and ONNX Runtime mwrap integration; runtime/build-engine changes are handled only if an actual integration failure requires them.