Add Codespaces configuration

Author: veithen

.devcontainer/devcontainer.json

@@ -0,0 +1,13 @@
+{
+	"image": "mcr.microsoft.com/devcontainers/base:ubuntu-22.04",
+	"features": {
+		"ghcr.io/devcontainers/features/java:1": {
+			"version": "8",
+			"installMaven": "true",
+			"mavenVersion": "3.9.1"
+		}
+	},
+	"hostRequirements": {
+		"memory": "8gb"
+	}
+}