add docker & build file

.space.kts

@@ -0,0 +1,17 @@
+job("Docker") {
+    host("Build and push a Docker image") {
+        shellScript {
+            content = """
+                export DOCKER_CLI_EXPERIMENTAL=enabled;
+                docker buildx create --name boxitkeycloak || true 2>/dev/null;
+                docker buildx use boxitkeycloak;
+                docker buildx build \
+                --platform linux/arm64,linux/amd64 \
+                --tag boxi.registry.jetbrains.space/p/boxit/containers/boxit-keycloak:0.0.${"$"}JB_SPACE_EXECUTION_NUMBER \
+                --push \
+                .;
+            """.trimIndent()
+        }
+    }
+}
+