VSCode: Add vcpkg toolchain file to settings.json (CMake Tools extension)

[SuperWig]

The following could be added to the settings.json for CMake Tools to use the vcpkg toolchain file.

"cmake.configureSettings": {
    "CMAKE_TOOLCHAIN_FILE": "${workspaceFolder}/vcpkg/scripts/buildsystems/vcpkg.cmake"
}

[StephanTLavavej]

Since you're proposing a specific change, can you submit this as a PR?

[SuperWig]

Sure, I wasn't sure which would be better as providing support for an external (to this project at least) extension, figured that might warrant a discussion, Then again that could be done in the PR 🤷‍♂️.