package.json scripts don't run on Windows

Created by: JoshuaKGoldberg

Windows requires set ENV_VAR_NAME=value. Mac/Linux allow ENV_VAR_NAME=value. In package.json:

// ...
"test": "TS_NODE_COMPILER_OPTIONS='{\"module\":\"commonjs\"}' mocha --require ts-node/register --require src/util/long-stack-traces.ts --timeout 10000 'src/**/*.test.ts?(x)'",
"cover": "TS_NODE_COMPILER_OPTIONS='{\"module\":\"commonjs\"}' nyc --require ts-node/register mocha --timeout 10000 './src/**/*.test.ts?(x)'",
// ...