docs: add changelog and roadmap files in English and Chinese

docs/en/06-changelog.md

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+---
+title: Changelog
+description: Release notes and updates for Obsidian to NotionNext
+---
+
+# Changelog
+
+Welcome to the Changelog for Obsidian to NotionNext! Here you'll find a detailed list of all the updates, improvements, and bug fixes made to the plugin over time from the version `2.7.0` onwards.

docs/en/07-roadmap.md

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+---
+title: Roadmap
+description: Planned features and improvements for Obsidian to NotionNext
+---
+
+# Roadmap
+
+- [ ] Automatic Syncing: Implement automatic syncing of notes at regular intervals or upon changes.
+- [ ] File Attachments: Support for syncing file attachments from Obsidian to Notion.
+- [ ] Relation Property: Enable mapping of Obsidian links to Notion relation properties.

docs/zh/06-changelog.md

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+---
+title: 更新日志
+description: Obsidian to NotionNext 的版本更新与变更记录
+---
+
+欢迎来到 Obsidian to NotionNext 的更新日志！这里会记录自 `2.7.0` 版本起的所有更新、改进以及问题修复，方便你快速了解插件的演进情况。

docs/zh/07-roadmap.md

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+---
+title: 路线图
+description: Obsidian to NotionNext 的规划功能与未来改进
+---
+
+- [ ] 自动同步：支持按时间间隔或内容变更自动同步笔记。
+- [ ] 附件支持：允许将 Obsidian 笔记中的附件一同上传到 Notion。
+- [ ] 关联属性：实现将 Obsidian 链接映射到 Notion 的 relation 属性。