Add runBackup function

[AdrienWalkowiak]

This is a function I created to run JIRA backups from an AWS lambda function (it could also be used from any node app obviously).

All it does, is checking in Webdav if a backup for today exists (HEAD request), returns it URI if it's the case and try to run the runBackup API function (POST) in JIRA to generate if otherwise and returns the new backup URI if successful.

[KanoYugoro]

This repo hasn't gotten any support in quite some time. You may want to check out our fork which is more up to date:

https://github.com/jira-node/node-jira-client https://www.npmjs.com/package/jira-client