The 'Getting Started Doc' should use CMake as the primary way to build and use Boost

This the build system that most people use so our documentation should cater to these folks. VCPkg consumption of the library should also get a nod since this is growing in popularity.

I found [tvision's CMake build instructions](https://github.com/magiblot/tvision) to be fairly good so you may take inspiration from there.

Locate the Getting Started document in this repository and review its current build instructions. Compare the proposed CMake guidance with tvision’s linked instructions, then include vcpkg consumption as a secondary path. Done means the guide presents CMake as the primary build method and gives vcpkg a useful mention.

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