Run the tests nightly (#103)

This is to ensure that we continue to have confidence that the
functionality works, and so that we are alerted to any regressions.

Using the [GitHub Actions scheduler functionality][1]

Closes #33

[1]: https://docs.github.com/en/actions/reference/events-that-trigger-workflows#scheduled-events

.github/workflows/integration_test.yml

@@ -1,5 +1,9 @@
 ---
-on: [push]  # yamllint disable-line rule:truthy
+on:  # yamllint disable-line rule:truthy
+  # Run the tests on every push, and also at 3am every night
+  push:
+  schedule:
+    - cron: '0 3 * * *'  # * is a special character in YAML so you have to quote this string
 name: Tests
 jobs:
   tests:

.github/workflows/virtual_test.yml

@@ -1,5 +1,9 @@
 ---
-on: [push]  # yamllint disable-line rule:truthy
+on:  # yamllint disable-line rule:truthy
+  # Run the tests on every push, and also at 3am every night
+  push:
+  schedule:
+    - cron: '0 3 * * *'  # * is a special character in YAML so you have to quote this string
 name: Tests
 jobs:
   tests: