Merge pull request #1 from lexbailey/main

I don't have push access to this repo. Can you add me? for now, here's a change that makes the CI work

.github/workflows/build_2023.yml

@@ -0,0 +1,13 @@
+on: [push]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    name: Build Theory
+    steps:
+      - uses: actions/checkout@v3
+      - uses: lexbailey/isabelle-theory-build-github-action@v8
+        with:
+          isabelle-url: 'https://github.com/seL4/isabelle/archive/refs/tags/Isabelle2023.tar.gz'
+          depends: 'https://github.com/isabelle-utp/Shallow-Expressions.git@main'
+          report_url: 'https://isabelle-utp-ci-dashboard.link/submit_job_log'
+          report_secret: ${{ secrets.DashboardReportKey }}