docs: update amalgamation instructions and add github action #3

	name: Amalgamation

	on: [check_run, push, pull_request]

	env:
	FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true

	jobs:
	amalgamation:
	runs-on: ubuntu-latest

	steps:
	- name: checkout project
	uses: actions/checkout@v4

	- name: setup python
	uses: actions/setup-python@v5
	with:
	python-version: '3.x'

	- name: run amalgamate script
	run: \|
	python amalgamate.py

	- name: test compile amalgamated source
	run: \|
	cat << 'EOF' > test_amalgamation.cpp
	#include "json/json.h"
	#include <iostream>

	int main() {
	Json::Value root;
	root["hello"] = "world";
	std::cout << root.toStyledString() << std::endl;
	return 0;
	}
	EOF
	c++ -std=c++11 -I dist dist/jsoncpp.cpp test_amalgamation.cpp -o test_amalgamation
	./test_amalgamation

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