projinfo as library function

[jjimenezshaw]

The main purpose if this PR is to allow the usage of projinfo as a library, not only as a CLI program.
That allows to call it, for instance, in the browser. See an example at https://jjimenezshaw.github.io/wasm-proj/projinfo.html

The code from the CLI was kept unmodified. To replicate the usage of std::cout and std::cerr, streams are used internally in the library, and the API is using a callback to report every call to those streams. See that some commands, like --list-crs can be very fragmented, with many calls to the callback.

For the specific usage of the callback in emscripten, a nicer helper in C++ is added to the build_wasm.sh script. That makes the usage from javascript much simpler and small.

I was not sure about the file structure to be used, and how to do it in CMake. Please, make any suggestion on that regard.

• AI/LLM (Copilot, ChatGPT, Claude or something similar) supported my development of this PR
• Closes #xxxx
• Tests added
• Added clear title that can be used to generate release notes
• Fully documented, including updating docs/source/*.rst for new API: Where and what exactly?

[jjimenezshaw]

The code in master is considering --help an error, and returns 1 (probably because it was simpler)
I kept the same behaviour in the code, but it is easy to change with this.

Suggested change

	return usage(strm);
	usage(strm);
	return 0;

Should I do it?

[jjimenezshaw]

cc @willcohen