CI: run cargo doc (#309)

* Deny doc errors

* Add intentional bad intradoc link to test CI

* Add cargo doc to CI

* Fix carg doc web (add wasm32 target)

* Fix intentionally broken doc-link

.github/workflows/rust.yml

@@ -120,3 +120,30 @@ jobs:
         with:
           command: clippy
           args: -- -D warnings
+
+  doc:
+    name: cargo doc
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - run: sudo apt-get install libspeechd-dev
+      - run: cargo doc -p emath -p epaint -p egui -p eframe -p epi -p egui_web -p egui_glium --lib --no-deps --all-features
+
+  doc_web:
+    name: cargo doc web
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - run: sudo apt-get install libspeechd-dev
+      - run: rustup target add wasm32-unknown-unknown
+      - run: cargo doc -p egui_web --target wasm32-unknown-unknown --lib --no-deps --all-features