CI Update (#91)

* https://github.com/crazy-max/ghaction-github-pages/releases

* https://github.com/actions/virtual-environments#available-environments

Author: juancarlospaco

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
         include:
           - target:
               os: linux
-            builder: ubuntu-18.04
+            builder: ubuntu-20.04
           - target:
               os: macos
             builder: macos-10.15
@@ -121,7 +121,7 @@ jobs:
           github.event_name == 'push' && github.ref == 'refs/heads/master' &&
           matrix.target.os == 'linux' && matrix.target.cpu == 'amd64' &&
           matrix.branch == 'devel'
-        uses: crazy-max/ghaction-github-pages@v1
+        uses: crazy-max/ghaction-github-pages@v2
         with:
           build_dir: fusion/htmldocs
           target_branch: gh-pages