Prototype a continuous integration workflow

This workflow is too spendthrift for deployment: every job sets up Rust,
and the `build` job also installs Trunk, which takes even more
resources. The workflow serves well, however, as a proof of concept.
Introducing a syntax error into `src/main.rs` causes the `build` and
`test` jobs to fail, but allows `run-examples` to succeed. Similarly,
introducing a syntax error into `examples/point-on-sphere.rs` causes
`run-examples` to fail, but allows the other jobs to succeed.

.forgejo/workflows/continuous-integration.yaml

@@ -0,0 +1,25 @@
+on:
+  pull_request:
+  push:
+    branches: [main]
+jobs:
+  build:
+    runs-on: docker
+    steps:
+      - uses: https://code.forgejo.org/actions/checkout@v4
+      - uses: ./.forgejo/setup-rust
+      - run: rustup target add wasm32-unknown-unknown
+      - run: cargo install trunk
+      - run: cd app-proto; trunk build
+  test:
+    runs-on: docker
+    steps:
+      - uses: https://code.forgejo.org/actions/checkout@v4
+      - uses: ./.forgejo/setup-rust
+      - run: cd app-proto; cargo test
+  run-examples:
+    runs-on: docker
+    steps:
+      - uses: https://code.forgejo.org/actions/checkout@v4
+      - uses: ./.forgejo/setup-rust
+      - uses: ./.forgejo/run-examples