add egg for runescape: dragonwilds (#495)

[euno-sbs]

Description

This is my first attempt at creating an egg, I took heavy inspiration from the other steamCMD game eggs and updated a version of them to work for Runescape: Dragonwilds.

I believe I have completed everything required to the best of my ability, but since it is my first time I would appreciate any feedback or support in correcting any errors I have made.

This resolves request (#495)

Checklist for all submissions

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you tested and reviewed your changes with confidence that everything works?
• Did you branch your changes and PR from that branch and not from your master branch?
  • If not, why?:

• You verify that the start command applied does not use a shell script
  • If some script is needed then it is part of a current yolk or a PR to add one
• The egg was exported from the panel

New egg Submissions

1. Does your submission pass tests (server is connectable)?
2. Does your egg use a custom docker image?
   • Have you tried to use a generic image?
   • Did you PR the necessary changes to make it work?
3. Have you added the egg to the main README.md and any other README files in subdirectories of the egg according to the alphabetical order?
4. Have you added a unique README.md for the egg you are adding according to the alphabetical order?
5. You verify that the start command applied does not use a shell script
   • If some script is needed then it is part of a current yolk or a PR to add one
6. The egg was exported from the panel