ci: update to python 3.8

Author: sgratzl

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v1
         with:
-          python-version: '3.7'
+          python-version: '3.8'
       - uses: actions/setup-node@v1
         with:
           node-version: '12.x'