Add vcpkg installation instructions

[FrankXie05]

bde is available as a port in vcpkg, a C++ library manager that simplifies installation for bde and other project dependencies. Documenting the install process here will help users get started by providing a single set of commands to build bde, ready to be included in their projects.

We also test whether our library ports build in various configurations (dynamic, static) on various platforms (OSX, Linux, Windows: x86, x64) to keep a wide coverage for users.

I'm a maintainer for vcpkg, and here is what the port script looks like. We try to keep the library maintained as close as possible to the original library.😊

[osubboo]

1. Those instructions do not work (tried from powershell & git bash):
   .\vcpkg.exe install bde
   Computing installation plan...
   A suitable version of cmake was not found (required v3.24.0). Downloading portable cmake v3.24.0...
   Downloading cmake...
   https://github.com/Kitware/CMake/releases/download/v3.24.0/cmake-3.24.0-windows-i386.zip -> C:\Users\osubbotin\work\vcpkg\vcpkg\downloads\cmake-3.24.0-windows-i386.zip
   Extracting cmake...
   bde[core]:x86-windows is only supported on '!windows & !arm'

2. Port script uses waf build system that is not supported for a few years now.
   This probably means that this port uses very old BDE code base (3.2.0 as I see; waf does not work with the current version of bde (3.107.0)).