Run tests workflow once / week + ignore non-code files in PRs (#6)

* Schedule tests workflow to run once per week

* Ignore changes to non-code files in PRs

.github/workflows/tests.yml

@@ -7,6 +7,13 @@ on:
   pull_request:
     paths-ignore:
       - "**.md"
+      - "**.rst"
+      - "**.svg"
+      - "docs/**"
+      - "CITATION.cff"
+      - "LICENSE"
+  schedule:
+    - cron: "0 0 * * 1"
 
 jobs:
   tests:
@@ -39,4 +46,4 @@ jobs:
         run: python -m pip install tox tox-gh-actions
 
       - name: Test with tox
-        run: tox
+        run: tox