Add DOCUMENTER_KEY to workflow config

.github/workflows/docs.yml

@@ -20,4 +20,5 @@ jobs:
       - name: Build and deploy
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          DOCUMENTER_KEY: ${{ secrets.DOCUMENTER_KEY }}
         run: julia --project=docs --color=yes docs/make.jl