ci: add load_all() test to make sure package works

.github/workflows/ci.yaml

@@ -0,0 +1,26 @@
+name: ci
+
+on:
+  push:
+    branches:
+      - "main"
+  pull_request:
+    branches:
+      - "main"
+
+jobs:
+  load:
+    runs-on: ubuntu-22.04
+    if: github.event_name == 'pull_request'
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup R
+        uses: r-lib/actions/setup-r@v2
+      - name: Setup R Dependencies
+        uses: r-lib/actions/setup-r-dependencies@v1
+        with:
+          extra-packages: |
+            devtools
+      - name: Load
+        run: R -e 'devtools::load_all()'