[mxml] New Port

[Rossmaxx]

fixes: #19042

• Changes comply with the maintainer guide.
• The name of the port matches an existing name for this component on https://repology.org/ if possible, and/or is strongly associated with that component on search engines.
• Optional dependencies are resolved in exactly one way. For example, if the component is built with CMake, all find_package calls are REQUIRED, are satisfied by vcpkg.json's declared dependencies, or disabled with CMAKE_DISABLE_FIND_PACKAGE_Xxx.
• The versioning scheme in vcpkg.json matches what upstream says.
• The license declaration in vcpkg.json matches what upstream says.
• The installed as the "copyright" file matches what upstream says.
• The source code of the component installed comes from an authoritative source.
• The generated "usage text" is accurate. See adding-usage for context.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Only one version is in the new port's versions file.
• Only one version is added to each modified port's versions file.

[Rossmaxx]

Do note that this PR is incomplete. I don't really know what I'm doing here, so any docs and extra help and info appreciated. Most of what's written here is copied from other ports.

[Rossmaxx]

What's with the license fail?

[FrankXie05]

@Rossmaxx Thanks for this PR. I think we need to ask upstream whether to add it to vcpkg. In this way, I can help you complete this PR. :)

[Rossmaxx]

I think we need to ask upstream whether to add it to vcpkg

I did ask about this upstream some time ago, and here's what the maintainer said. Forgot that i asked this in the first place.

michaelrsweet/mxml#281 (comment)

I initially asked for cmake support but the maintainer refused. It's after some time that I understand that vcpkg doesn't require ports to be in cmake and other build systems being supported.

I personally need this port for a project which I'm involved with. I'm trying to add msvc support for a previously mingw built application.

For my use case, I am thinking of disabling linux ports as I don't really want to deal with pkg config here. I'll update the vckpg.json when i start working on this again. I'm on a small break now. But i would like to collect as much info on this break.

Thanks for your reply.

[dg0yt]

Suggested change

	"license": "Apache license 2.0"
	"license": "Apache-2.0"

[dg0yt]

(I don't understand the comments about upstream. No patches, no restriction, no need to ask.)