chore: re-enable julia nightly in ci

CI with nightlies were disabled earlier because of instabilities. It will be good to enable CI with julia nightlies back again, since #82 needs Downloads.jl version that's included only in the nightlies at the moment.

Author: tanmaykm

.github/workflows/ci.yml

@@ -14,6 +14,7 @@ jobs:
         version:
           - '1.6'
           - '1' # automatically expands to the latest stable 1.x release of Julia
+          - 'nightly'
         os:
           - ubuntu-latest
         arch: