Added a batch-script that uploads tgstation.rsc to an external FTP-server

Added a batch-script to easily upload **tgstation.rsc** to an external FTP-server, for use with **external_rsc_url.txt**.

**Run this script every time you have compiled your code if you are using external_rsc_url.txt, otherwise players will get errors when joining.**

Edit the batch-script with your login details
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* Replace **USERNAME** with your FTP username
* Replace **PASSWORD** with your FTP password
* Replace **FOLDER/FOLDER** with the folder on the FTP server where you want to store **tgstation.rsc**, for example: **cd www/rsc**
* Replace **FTP.DOMAIN.COM** with the IP-address or domain name of your FTP server
* Add the URL to the location of **tgstation.rsc** on your webserver into **data\external_rsc_urls.txt**