Use /dev/stdin instead of 0 when using with readFileSync

[ben-z]

Sometimes, especially when reading large inputs from stdin, we get the following error:

node:internal/fs/sync:25
  return binding.readFileUtf8(path, stringToFlags(flag));
                 ^

Error: EAGAIN: resource temporarily unavailable, read
    at Object.readFileUtf8 (node:internal/fs/sync:25:18)
    at Object.readFileSync (node:fs:441:19)
    at /usr/local/lib/node_modules/@watonomous/watcloud-emails/dist/cli/index.js:74:44
    at Generator.next (<anonymous>)
    at /usr/local/lib/node_modules/@watonomous/watcloud-emails/dist/cli/index.js:9:71
    at new Promise (<anonymous>)
    at __awaiter (/usr/local/lib/node_modules/@watonomous/watcloud-emails/dist/cli/index.js:5:12)
    at Command.<anonymous> (/usr/local/lib/node_modules/@watonomous/watcloud-emails/dist/cli/index.js:69:41)
    at Command.listener [as _actionHandler] (/usr/local/lib/node_modules/@watonomous/watcloud-emails/node_modules/commander/lib/command.js:542:17)
    at /usr/local/lib/node_modules/@watonomous/watcloud-emails/node_modules/commander/lib/command.js:1502:14 {
  errno: -11,
  code: 'EAGAIN',
  syscall: 'read'
}

This appears to be because process.stdin.fd only operates on nonblocking mode. This PR accesses /dev/stdin directly instead of using 0.

References:

• https://stackoverflow.com/a/75948127/4527337