Add Multi-Language Descriptions for 'Switch' Component and Update Message Assistant Placeholder (#2450)

### What problem does this PR solve?

_This PR addresses the need to describe the "Switch" component across
different languages and corrects a misleading description for a
placeholder message not exclusively tied to a specific assistant type.
By providing clearer and more accurate descriptions, this PR aims to
improve user understanding and usability of the Switch component and the
"Message Resume Assistant..." placeholder in a multilingual context._

### Explanation of Changes

1. **Added Descriptions for "Switch" Component**: 
- Descriptions were added for the "Switch" component in three different
locales:
- **English (EN)**: Provides a concise description of what the "Switch"
component does, focusing on its ability to evaluate conditions and
direct the flow of execution.
- **Simplified Chinese (ZH)**: Translated the English description into
Simplified Chinese to cater to users who prefer this locale.
- **Traditional Chinese (ZH-Traditional)**: Added a Traditional Chinese
version of the description to support users in regions that use
Traditional Chinese.
   
2. **Corrected "Message Resume Assistant..." to "Message the
Assistant..."**:
- Updated the description from "Message Resume Assistant..." to "Message
the Assistant..." in the English locale. This correction makes the
description more generic and accurate, reflecting the placeholder's
broader functionality, which is not limited to Resume Assistants. It now
clearly communicates that the placeholder can be used with various types
of assistants, not just those related to resumes.

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [x] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

web/src/locales/zh.ts

@@ -634,6 +634,7 @@ export default {
       messageDescription:
         '此组件用于向用户发送静态信息。您可以准备几条消息，这些消息将被随机选择。',
       keywordDescription: `该组件用于从用户的问题中提取关键词。Top N指定需要提取的关键词数量。`,
+      switchDescription: `该组件用于根据前面组件的输出评估条件，并相应地引导执行流程。通过定义各种情况并指定操作，或在不满足条件时采取默认操作，实现复杂的分支逻辑。`,
       wikipediaDescription: `此组件用于从 https://www.wikipedia.org/ 获取搜索结果。通常，它作为知识库的补充。Top N 指定您需要调整的搜索结果数量。`,
       promptText: `请总结以下段落。注意数字，不要胡编乱造。段落如下：
 {input}