Add Ubuntu 19.04 images for 3.0 #1081
Description
- This only applies to 3.0 and will not be back ported to 2.x
- Once 19.10 is released, we will add 19.10 images. 19.04 images will be supported for 3 more months before being dropped. The same thing will happen once 20.04 (LTS) is released - 20.04 images will be added and the 19.10 images will be supported for 3 more months before being dropped.
- Support will remain for Bionic (18.04) throughout the lifetime of .NET Core 3.0.