Install gpio-sim to github runner

Now that there's a test that uses gpio-sim, we need the kernel module in
the runner environment for it to work.

.github/workflows/ci.yml

@@ -15,6 +15,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Install gpio-sim
+        run: |
+          sudo apt-get update
+          sudo apt-get install linux-modules-extra-$(uname -r)
+          sudo modprobe gpio-sim
       - name: Build
         run: cargo build --verbose
       - name: Run fmt