Replace README.md with package-info.java in converter package

Signed-off-by: stroller <fujian1115@gmail.com>

Author: jiafu1115

spring-ai-model/src/main/java/org/springframework/ai/converter/README.md

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2023-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Provides converters for transforming AI model text outputs into structured Java types.
+ *
+ * <p>
+ * The output of AI models traditionally arrives as a {@code String}, even if you ask for
+ * the reply to be in JSON. This package provides specialized converters that employ
+ * meticulously crafted prompts and parsing logic to convert text responses into usable
+ * data structures for application integration.
+ *
+ * <p>
+ * For detailed documentation and usage examples, see the <a href=
+ * "https://docs.spring.io/spring-ai/reference/api/structured-output-converter.html">Structured
+ * Output Converter Reference Guide</a>.
+ */
+@NonNullApi
+@NonNullFields
+package org.springframework.ai.converter;
+
+import org.springframework.lang.NonNullApi;
+import org.springframework.lang.NonNullFields;