fix: ability to process package-lock.json with more than 1024*1024 bytes

[DudaGod]

Problem

In the case when you have package-lock.json is more than 1048576 (1024 * 1024) bytes child process fails with error here - https://github.com/npm/npm-merge-driver/blob/latest/index.js#L195-L201. Error:

Error: spawnSync git ENOBUFS
    at Object.spawnSync (internal/child_process.js:1041:20)
    at Object.spawnSync (child_process.js:616:24)
    at Object.merge [as handler] (/Users/dudkevich/job/projects/third-party/npm-merge-driver/index.js:206:18)
    at Object.runCommand (/Users/dudkevich/job/projects/third-party/npm-merge-driver/node_modules/yargs/lib/command.js:228:22)
    at Object.parseArgs [as _parseArgs] (/Users/dudkevich/job/projects/third-party/npm-merge-driver/node_modules/yargs/yargs.js:1013:30)
    at Object.get [as argv] (/Users/dudkevich/job/projects/third-party/npm-merge-driver/node_modules/yargs/yargs.js:957:21)
    at parseArgs (/Users/dudkevich/job/projects/third-party/npm-merge-driver/index.js:93:21)
    at Object.<anonymous> (/Users/dudkevich/job/projects/third-party/npm-merge-driver/index.js:11:3)
    at Module._compile (internal/modules/cjs/loader.js:1138:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1158:10) {
  errno: 'ENOBUFS',
  code: 'ENOBUFS',
  syscall: 'spawnSync git',
  path: 'git',
  spawnargs: [
    'merge-file',
    '-p',
    '.merge_file_D1OBa2',
    '.merge_file_dX2qR6',
    '.merge_file_I14Rra'
  ]
}

To fix it I increase maxBuffer to Infinity and add error handler for child process in order to exit if something goes wrong.

Environment:

node: 12.18.0
npm: 6.14.5
git: 2.29.1