Update GitHub workflow

* Run workflow on pull request as well as push
* Run workflow on matrix of 3 different OS
* Use actions/cache to speed up the build

.github/workflows/build.yml

@@ -2,33 +2,59 @@ name: CI
 
 on:
   push:
-    branches:
-      - main
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macOS-latest]
     steps:
       - uses: actions/checkout@v3
         with:
           submodules: 'recursive'
+
+      - uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
       - name: Setup prerequisites
         shell: bash
+        if: matrix.os == 'ubuntu-latest'
         run: |
           sudo apt update
           sudo apt install lzop
+
+      - name: Setup prerequisites
+        shell: bash
+        if: matrix.os == 'macOS-latest'
+        run: |
+          brew install lzop
+
       - name : Toolchain info
         run: |
           cargo --version --verbose
           rustc --version --verbose
+
       - name: Run cargo build
         run: |
           cargo build --release
+
       - name: Run cargo clippy
         run: |
           cargo clippy
         env:
           CI: true
+
       - name: Run cargo test
         run: |
           cargo test --release --test integration  -- --show-output