LDC 1.13.0-beta1

[kinke]

Glad to announce the first beta for LDC 1.13:

* Based on D 2.083.0.
* The Windows packages are now fully self-sufficient, i.e., a 
Visual Studio/C++ Build Tools installation isn't required anymore.
* Substantial debug info improvements for GDB.

Full release log and downloads: 
https://github.com/ldc-developers/ldc/releases/tag/v1.13.0-beta1

Thanks to all contributors!