Add vcpkg installation instructions

[Cheney-W]

H3 available as a port in vcpkg, a C++ library manager that simplifies installation for H3 and other project dependencies. Documenting the install process here will help users get started by providing a single set of commands to build H3, 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.

[CLAassistant]

All committers have signed the CLA.

[dfellis]

I don't know if I want to endorse this "vcpkg" tool in the repo like this. The H3 version it installs is several years out of date and it is making opinionated decisions for users like deleting all of the utility binaries.

[coveralls]

Coverage remained the same at 99.038% when pulling 77f7272 on Cheney-W:vcpkg-instructions into 619a2a7 on uber:master.

[nrabinowitz]

I don't know if I want to endorse this "vcpkg" tool in the repo like this. The H3 version it installs is several years out of date and it is making opinionated decisions for users like deleting all of the utility binaries.

I don't see how this is significantly different from including Homebrew installation instructions? This seems fine to me, users who don't want a somewhat opinionated package manager have other options.

I agree that it would be great to at least install v3.7.2 (the latest H3 v3 release).

[Cheney-W]

I saw the latest release of h3 is v4.0.0, I will update this port to this version.