TEST: Peform GitHub testing with Pythons 3.8-3.11

Also, run `pip install --upgrade typing-extensions` on GitHub after
installing the tensorflow dependency of histomics_stream because
tensorflow under Python 3.8 inappropriately downgrades
typing-extensions and that breaks a dependency of large_image.

.github/workflows/build-test-package.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       max-parallel: 2
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9"]
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
 
         include:
           - flake8-python-git-tag: ""
@@ -42,6 +42,10 @@ jobs:
       - name: Install histomics_stream
         run: |
           pip install .[tensorflow,torch,zarr]
+          # With Python 3.8, tensorflow downgrades typing-extensions, which appears to
+          # be unnecessary and breaks a dependency of large_image, so we overrule that
+          # next.
+          pip install --upgrade typing-extensions
 
       - name: Lint with flake8
         run: |