message: [now-cli] Print error during install for unsupported Node version
  Fixes
  ### Output
  ```
  > preinstall /usr/local/lib/node_modules/now
  > node ./scripts/preinstall.js
  > Error! Detected unsupported Node.js version.
  Expected ">= 10" but found "8.10.0".
  Please update to the latest Node.js LTS version to install Now CLI.
  ```
diff: @@ -81,12 +81,39 @@ async function isBinary(nowPath) {
  return !stats.isDirectory();
  }
  +function validateNodeVersion() {
  + let semver = '>= 0';
  + let major = '1';
  +
  + try {
  + major = process.versions.node.split('.')[0];
  + const pkg = require('../package.json');
  + semver = pkg.engines.node;
  + } catch (e) {
  + debug('Failed to read package.json engines');
  + }
  +
  + const isValid = eval(`${major} ${semver}`);
  + return { isValid, expected: semver, actual: process.versions.node };
  +}
  +
  async function main() {
  if (!isGlobal()) {
  debug('Skip preinstall since now is being installed locally');
  return;
  }
  + const ver = validateNodeVersion();
  +
  + if (!ver.isValid) {
  + error(
  + `Detected unsupported Node.js version.\n` +
  + `Expected "${ver.expected}" but found "${ver.actual}".\n` +
  + `Please update to the latest Node.js LTS version to install Now CLI.`
  + );
  + process.exit(1);
  + }
  +
  const nowPath = getNowPath();
  if (nowPath === null) {
  