[docs] The correct adderss can't access

[PhoebeHui]

https://vcpkg.io/en/docs/users/config-environment.html

Environment and Configuration ->VCPKG_OVERLAY_PORTS

The links for ports-overlay can't access, however, the adderss is correct, and it can access in original docs https://github.com/microsoft/vcpkg/blob/master/docs/users/config-environment.md#vcpkg_overlay_ports.

So this may be a problem that navigate to the 'Ports Overlay' node in the left navigation bar

The original docs: https://github.com/microsoft/vcpkg/blob/master/docs/specifications/ports-overlay.md
The address provided by the website https://vcpkg.io/en/docs/specifications/ports-overlay.md

Similar issue for the VCPKG_OVERLAY_TRIPLETS and Feature Packages in Further reading

Related to #26 (comment)
#26 (comment)