Test against Python 3.10 in CI

Workflow will still succeed if Python 3.10 jobs fail.

Author: duckontheweb

.github/workflows/continuous-integration.yml

@@ -14,6 +14,7 @@ jobs:
   test:
     name: test
     runs-on: ${{ matrix.os }}
+    continue-on-error: ${{ startsWith(matrix.python-version, '3.10')}}
     strategy:
       # Allow other matrix jobs to complete if 1 fails
       fail-fast: false
@@ -23,6 +24,7 @@ jobs:
           - "3.7"
           - "3.8"
           - "3.9"
+          - "3.10.0-beta.3"
         os:
           - ubuntu-latest
           - windows-latest

README.md

@@ -10,6 +10,9 @@ PySTAC is a library for working with [SpatialTemporal Asset Catalog](https://sta
 
 ## Installation
 
+PySTAC requires Python>=3.6. Support for Python>=3.10 should be considered experimental
+until further notice.
+
 PySTAC has a single required dependency (`python-dateutil`).
 PySTAC can be installed from pip or the source repository.