workflow(test): install opus before building

Author: anunaym14

.github/workflows/buildtest.yaml

@@ -35,6 +35,11 @@ jobs:
             ~/go/bin
             ~/.cache
           key: server-sdk-go
+      
+      - name: Setup Opus
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libopus-dev libopusfile-dev opus-tools
 
       - name: Set up Go
         uses: actions/setup-go@v5