Add toolset=msvc-143 (Visual Studio 2022) to B2 user manual

From: Kenneth Porter (shiva_at_[hidden])
Date: 2023-03-27 02:54:27

I was looking up the syntax to add MSVS 2022 to my library build script and 
the online manual lacks it:

<https://www.boost.org/doc/libs/1_81_0/tools/build/doc/html/index.html#bbv2.reference.tools.compilers>

I don't know where the repo is for this page or I'd file an issue. Perhaps 
include the repo link at the top or bottom of the page or in an HTML 
comment?