Add VisionOS support to Swift Package Manager Package.swift definition file

[richardtop]

Since the release of Apple Vision Pro hardware, it's now possible to run C++ code when targeting Vision OS. This change enables support for VisionOS in this package, so that the C++-based products can now leverage this library when being built for the AVP hardware.

• The changes are described in detail, both the what and why.
• If applicable, an existing issue is referenced.
• The Code coverage remained at 100%. A test case for every new line of code.
• If applicable, the documentation is updated.
• The source code is amalgamated by running make amalgamate.

Read the Contribution Guidelines for detailed information.

[coveralls]

coverage: 99.186%. remained the same
when pulling 6e58eaf on richardtop:vision_os_spm_support
into f06604f on nlohmann:develop.

[nlohmann]

Please check https://github.com/nlohmann/json/pull/4611/checks?check_run_id=35854078785 on how to resolve the DCO warning.

[richardtop]

@nlohmann Please check, I've fixed this, I'm not sure why this dco action is failing now.

[nlohmann]

This is from the DCO action:

Commit sha: 645a834, Author: Richard Topchii, Committer: Richard Topchii; Expected "Richard Topchii [email protected]", but got "Richard Topchii [email protected]".

[richardtop]

Clear, so the emails must match. I'm adjusting this now.

[richardtop]

@nlohmann Please check again, I've finally fixed this issue with your suggestion.

[nlohmann]

Looks good to me.

[nlohmann]

Thanks! Though I wonder if anyone would actually use this library in a Swift project.

[richardtop]

@nlohmann guess why this file got added here in the first place. The answer is "hell yeah!" and thanks for the great library.
In fact, I've demoed the way to integrate this library with a C++ project which later is integrated into Swift app: https://www.youtube.com/watch?v=DSLRObswE3Y