Add vcpkg installation instructions

[grdowns]

Avro is available as a port in vcpkg. Adding installation instructions will help users get started by providing a single set of commands they can use to build Avro and include it into their projects

[Fokko]

@blachniet, when you have time, could you shed some light on this?

@grdowns Could you create a ticket on Jira? We use Jira to generate the release logs.

[blachniet]

Before now, I had never heard of vcpkg. It sounds a bit like a Maven Central, npm, or NuGet, but for C++ projects. @grdowns, is that a fair comparison?

If my understanding of vcpkg is correct, then I don't think BUILD.md is the best place for these instructions. BUILD.md describes how to build the Avro project as an Avro developer, not a user. If vcpkg is specifically for C++ projects, maybe we could add this blurb to the C++ API page:

• Source: https://github.com/apache/avro/blob/2d3b1fe7efd865639663ba785877182e7e038c45/lang/c%2B%2B/MainPage.dox
• Page: http://avro.apache.org/docs/1.9.1/api/cpp/html/index.html

Here's some vcpkg resource I ran across in my very brief bit of research:

• Read The Docs: https://vcpkg.readthedocs.io/en/latest/
• GitHub Project: https://github.com/microsoft/vcpkg
• Avro Patch in vcpkg repo: https://github.com/microsoft/vcpkg/blob/7d72108b9a09e92342ff695c074766fb068049df/ports/avro-c/avro.patch