Port GasFreshdesk to NodeJS

[huan]

GasFreshdesk is write to modulize freshdesk api in google apps scripts, so It can't run by nodejs, also it is not packed to NPM yet.

However, I believe port to nodejs is quite easy, because code is clean and only need changes a few class from gas to nodejs. (i.e. UrlFetchApp, Utilities).

Also I like async library. It's better to keep GasFreshdesk to be async in nodejs.

Contribution is very welcome, because I mainly use GasFreshdesk inside gas.