docs(features): add inline chat documentation and reorganize custom language doc

- Added new documentation for inline chat feature under `docs/features/inline-chat.md`.
- Moved `custom-language.md` from `docs/customize/` to `docs/development/` and updated its parent section.

Author: phodal

docs/customize/custom-language.md renamed to docs/development/custom-language.md

@@ -1,7 +1,7 @@
 ---
 layout: default
 title: Custom Language
-parent: Customize Features
+parent: Development
 nav_order: 11
 permalink: /custom/language
 ---

docs/features/inline-chat.md

@@ -0,0 +1,12 @@
+---
+layout: default
+title: Inline Chat
+parent: Basic Features
+nav_order: 4
+permalink: /features/inline-chat
+---
+
+1. Select a code and click in editor Gutter
+2. Click AutoDev AI Chat
+
+<img src="https://unitmesh.cc/auto-dev/inline-chat.png" alt="Inline Chat" width="600px"/>