Add documents site (#1767)

* feat: add docs site

- Implemented dynamic routing for MDX documentation pages with language support.
- Created layout components for documentation with a header and footer.
- Added metadata for various documentation sections in English and Chinese.
- Developed initial content for the DeerFlow App and Harness documentation.
- Introduced i18n hooks and translations for English and Chinese languages.
- Enhanced header component to include navigation links for documentation and blog.
- Established a structure for tutorials and reference materials.
- Created a new translations file to manage locale-specific strings.

* feat: enhance documentation structure and content for application and harness sections

* feat: update .gitignore to include .playwright-mcp and remove obsolete Playwright YAML file

* fix(docs): correct punctuation and formatting in documentation files

* feat(docs): remove outdated index.mdx file from documentation

* fix(docs): update documentation links and improve Chinese description in index.mdx

* fix(docs): update title in Chinese for meta information in _meta.ts

frontend/src/content/en/tutorials/_meta.ts

@@ -0,0 +1,21 @@
+import type { MetaRecord } from "nextra";
+
+const meta: MetaRecord = {
+  "first-conversation": {
+    title: "First Conversation",
+  },
+  "create-your-first-harness": {
+    title: "Create Your First Harness",
+  },
+  "use-tools-and-skills": {
+    title: "Use Tools and Skills",
+  },
+  "work-with-memory": {
+    title: "Work with Memory",
+  },
+  "deploy-your-own-deerflow": {
+    title: "Deploy Your Own DeerFlow",
+  },
+};
+
+export default meta;

frontend/src/content/en/tutorials/create-your-first-harness.mdx

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+# Create Your First Harness
+
+TBD

frontend/src/content/en/tutorials/deploy-your-own-deerflow.mdx

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+# Deploy Your Own DeerFlow
+
+TBD

frontend/src/content/en/tutorials/first-conversation.mdx

@@ -0,0 +1,3 @@
+# First Conversation
+
+TBD

frontend/src/content/en/tutorials/use-tools-and-skills.mdx

@@ -0,0 +1,3 @@
+# Use Tools and Skills
+
+TBD

frontend/src/content/en/tutorials/work-with-memory.mdx

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+# Work with Memory
+
+TBD