ci: add feature powerset & style: used #[cfg(all(..))]

.github/workflows/build.yml

@@ -88,6 +88,19 @@ jobs:
         command: test
         args: ${{matrix.flags}}
 
+  feature_powerset:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        override: true
+    - uses: taiki-e/install-action@v2
+      with:
+        tool: cargo-hack@0.5.25
+    - run: cargo hack check --feature-powerset --depth 2 --no-dev-deps --exclude-features "stdweb wasm-bindgen f32_float"
+
   # no-std builds are a bit more extensive to test
   no_std_build:
     name: NoStdBuild