doc: about gradle java-version

Signed-off-by: CaiJingLong <cjl_spy@163.com>

docs/src/photo_manager/gradle/java-version/index.en.md

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+---
+title: "Configuring Java Version in photo_manager"
+weight: 1
+---
+
+To ensure compatibility with older versions of AGP/flutter SDK, `photo_manager` supports configuring the project's Java version through configuration files, environment variables, and other methods.
+
+It looks for the Java version in the following order:
+
+1. Configuration in `gradle.properties` using the `java.version` property. The value should be in the format of a Java version number, such as `1.8`, `11`, `17`, `21`, etc.
+2. Using the `JAVA_HOME` environment variable, which should point to the installation path of the JDK. Typically, the Java executable is located at `$JAVA_HOME/bin/java`.
+3. Configuration in `gradle.properties` using the `java.home` property.
+4. Reading the runtime property `java.home` of the JDK.
+5. If none of the above is found, it defaults to using `JavaVersion.current()`.
+
+Steps 4 and 5 should use the JDK configured in the Gradle settings, which is usually the same.

docs/src/photo_manager/gradle/java-version/index.zh.md

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+---
+title: "photo_manager 中 java version 的配置方式"
+weight: 1
+---
+
+photo_manager 为了保证旧版本 AGP/flutter SDK 的兼容性
+所以支持通过配置文件/环境变量等方式来配置项目的 java 版本
+
+它们会按照如下的顺序来查找 java 版本:
+
+1. 通过 `gradle.properties` 中的 `java.version` 配置，它的值应该是一个 java 版本号的字符格式
+   例如: `1.8` `11` `17` `21` 等
+2. 通过 `JAVA_HOME` 环境变量，它应该是一个 jdk 的安装路径，java 一般位于 `$JAVA_HOME/bin/java`
+3. 通过 `gradle.properties` 中的 `java.home` 来配置
+4. 通过读取 JDK 的运行时属性 `java.home` 来读取
+5. 如果以上都没有找到，那么会使用 JavaVersion.current()
+
+以上的4、5步骤应该使用的是 Gradle 配置中的 JDK，通常是相同的