Add system dependencies installation step in CI workflow

- Updated the GitHub Actions workflow to include a step for installing necessary system dependencies, ensuring the environment is properly set up for subsequent tasks.

Author: eliasjpr

.github/workflows/crystal.yml

@@ -14,6 +14,9 @@ jobs:
     steps:
       - uses: actions/checkout@v1
 
+      - name: Install system dependencies
+        run: apt-get update && apt-get install -y libreadline-dev libevent-dev libssl-dev libxml2-dev libyaml-dev libgmp-dev
+
       - name: Install dependencies
         run: shards install