chore(ci): run container and wait for it to connect (#2956)

- Added safety to prevent panics/errors when skipping CI checks (shame on me, sometimes)
- Opens new possibilities for end to end integration tests. PRs accepted!

ci/cmd/main.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+
+	"github.com/qdm12/gluetun/ci/internal"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Usage: " + os.Args[0] + " <command>")
+		os.Exit(1)
+	}
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
+
+	var err error
+	switch os.Args[1] {
+	case "mullvad":
+		err = internal.MullvadTest(ctx)
+	default:
+		err = fmt.Errorf("unknown command: %s", os.Args[1])
+	}
+	stop()
+	if err != nil {
+		fmt.Println("❌", err)
+		os.Exit(1)
+	}
+	fmt.Println("✅ Test completed successfully.")
+}