docs: add FAQ about title rendering issues when manually setting padding (#6554)

* docs: add FAQ about title rendering issues when manually setting padding

* docs: beautify FAQ document format

Author: BQXBQX

site/docs/manual/FAQ/index.en.md

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+---
+title: 'Frequently Asked Questions (FAQ)'
+order: 4
+---
+
+## Title Not Rendering After Manually Setting Padding
+
+### Problem Description
+
+When using AntV G2 to render charts, manually setting the `padding` can cause the chart title to not render properly or disappear entirely.
+
+Related issue: [Title is not displayed after setting](https://github.com/antvis/G2/issues/6549)
+
+### Cause Analysis
+
+G2 dynamically calculates the space required for all components by default, but once a fixed `padding` value is specified, this automatic adjustment logic is skipped, which may lead to incomplete rendering of the components.
+
+### Solutions
+
+There are two ways to resolve this issue:
+
+#### 1. Use the Default Layout (Recommended)
+
+Allow G2 to automatically calculate the optimal spacing to ensure that all components are rendered correctly:
+
+```javascript
+chart
+  .interval()
+  .encode('x', 'category')
+  .encode('y', 'value')
+  .encode('color', 'type');
+```
+
+#### 2. Set Padding Correctly
+
+If you must manually set the `padding`, make sure to reserve enough space for dynamically generated components:
+
+```javascript
+chart
+  .padding(50)
+  .interval()
+  .encode('x', 'category')
+  .encode('y', 'value')
+  .encode('color', 'type');
+```
+
+### Notes
+
+- When manually setting `padding`, it is recommended to debug and find the appropriate values.
+- Consider the space requirements for titles, legends, and other components.
+- If a specific layout is not required, it's better to use G2's automatic layout system.

site/docs/manual/FAQ/index.zh.md

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+---
+title: '常见问题 FAQ'
+order: 4
+---
+
+## 手动设置 Padding 后标题无法渲染
+
+### 问题描述
+
+在使用 AntV G2 绘制图表时，手动设置 `padding` 可能会导致图表标题无法正常显示或完全消失。
+
+相关问题：[设置完 title 不显示](https://github.com/antvis/G2/issues/6549)
+
+### 原因分析
+
+G2 默认会动态计算所有组件所需的间距，但一旦指定了固定的 `padding` 值，这个自动调整的逻辑就会被跳过，可能导致组件显示不完整。
+
+### 解决方案
+
+有两种方式可以解决这个问题：
+
+#### 1. 使用默认布局（推荐）
+
+让 G2 自动计算最佳间距，确保所有组件正常显示：
+
+```javascript
+chart
+  .interval()
+  .encode('x', 'category')
+  .encode('y', 'value')
+  .encode('color', 'type');
+```
+
+#### 2. 正确设置 Padding
+
+如果确实需要手动设置 `padding`，请确保为动态生成的组件预留足够空间：
+
+```javascript
+chart
+  .padding(50)
+  .interval()
+  .encode('x', 'category')
+  .encode('y', 'value')
+  .encode('color', 'type');
+```
+
+### 注意事项
+
+- 手动设置 `padding` 时，建议通过调试确定合适的数值
+- 需要考虑标题、图例等组件的空间需求
+- 在不需要特定布局时，优先使用 G2 的自动布局功能