Add samples readme

[kennykerr]

This adds a brief explanation for how to find the correct samples for a given release of the windows and windows-sys crates.

Fixes: #1977

[kennykerr]

Sigh. Cargo 1.46 - used to validate windows-sys - doesn't like a readme.md in the workspace.

[rylev]

@kennykerr what was the error you encountered? Seems strange that a markdown file would trip up cargo.

[ChrisDenton]

You may need to add an exclude to windows-rs/Cargo.toml otherwise it's matched by the crates/samples/* member. See the Cargo docs.

[kennykerr]

https://github.com/microsoft/windows-rs/runs/7976243489?check_suite_focus=true

[rylev]

@ChrisDenton's suggestion is exactly what you need to do:

[workspace]
members = [
  "samples/*",
  # ...
]
exclude = ["samples/readme.md"]

[kennykerr]

Its interesting that it works with newer versions of cargo, but that's a reasonable workaround - thanks!

[kennykerr]

This issue was also addressed some time between 1.46 and 1.49 so I think I'll just update the MSRV of windows-sys and avoid complicating the workspace. #1987

[riverar]

This particular issue was fixed in Cargo 1.47 (rust-lang/cargo#8511)