Update CI to add a test matrix for features

.github/workflows/rust.yml

@@ -28,20 +28,29 @@ jobs:
         with:
           command: check
 
-  test:
-    name: Test Suite
+  check_features:
+    name: Check features
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        features:
+          - --features=default
+          - --all-features
+          - --features=bigint,serialize,debug
+          - --features=bigint,serialize,trace
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal
           toolchain: stable
           override: true
+      - name: Cargo update
+        run: cargo update
       - uses: actions-rs/cargo@v1
         with:
           command: test
-          args: --all-features
+          args: ${{ matrix.features }}
 
   no_std:
     name: no-std