update devEngines to include nodejs 10.x

[dongyuwei]

Use nodejs v10.6.0 to run yarn install under react directory will throw an exception(triggered by the postinstall hook):

yarn install
yarn install v1.7.0
[1/4] 🔍  Resolving packages...
success Already up-to-date.
$ node node_modules/fbjs-scripts/node/check-dev-engines.js package.json && node ./scripts/flow/createFlowConfigs.js
assert.js:269
    throw err;
    ^

AssertionError [ERR_ASSERTION]: Current node version is not supported for development, expected "10.6.0" to satisfy "8.x || 9.x".
    at Object.<anonymous> (/Users/yuwdong/code/js/react/node_modules/fbjs-scripts/node/check-dev-engines.js:39:3)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
    at startup (internal/bootstrap/node.js:236:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:560:3)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.

Because in current package.json, the devEngines declaration is:

"devEngines": {
    "node": "8.x || 9.x"
  },

Can we think about also support nodejs 10.x as devEngine? Thanks.

[gaearon]

Thanks