CI for Julia 1.8 beta 1 (#804)

Author: fonsp

.github/workflows/ci.yml

@@ -18,6 +18,7 @@ jobs:
       fail-fast: false
       matrix:
         version:
+          - '~1.8.0-0' # 1.8 beta
           - '1.6'
           - '1' # automatically expands to the latest stable 1.x release of Julia
           - 'nightly'