Add vcpkg installation instructions

[FrankXie05]

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

[coveralls]

Coverage remained the same at 98.733% when pulling c4a9050 on FrankXie05:vcpkg-instructions into 0422cad on strasdat:master.

[FrankXie05]

Error form macos-10.15 https://github.com/strasdat/Sophus/runs/8264461555?check_suite_focus=true

/usr/local/include/fmt/core.h:1756:3: error: static_assert failed due to requirement 'formattable' "Cannot format an argument. To make type T formattable provide a formatter<T> specialization: https://fmt.dev/latest/api.html#udt"
  static_assert(
  ^

It looks like the reason for the failure is that the fmt library is passing a type that doesn't provide a formatting method. Is it because of the currently unsupported fmt version? 🤔

[FrankXie05]

@strasdat

[NikolausDemmel]

Yes, looks like #376 will need to be merged for CI succeed.

[FrankXie05]

PR #376 has been merged, reopen PR to rerun CI tests

[FrankXie05]

@strasdat This PR is ready for review.

[strasdat]

@FrankXie05, sorry it has been some time, and I just pushed a larger update (#538). If you are still interested, I'd be happy to coordinate...

[FrankXie05]

@strasdat Need me to do something? ：）

[strasdat]

@FrankXie05 thanks for the PR! I think I'm a little confused since I would have expected a vcpk.json in the root of the Sophus repository. Maybe it got deleted at some point...

Nevertheless, I tried out the instructions against the current port versions and they worked. Hence I will rebase your change and get the instructions in. I'll open an issue/PR against vcpkg later to update the version.