refactor: clean up dependencies and improve markdown rendering

- Removed unused dependencies: @bugsplat/elfy, @vue/shared, @neilsustc/markdown-it-katex, elfjs, elfy, and katex from package.json.
- Updated highlight.js usage to only register essential languages (C, C++, Python, JavaScript, TypeScript) for RT-Thread development in renderer.ts.
- Removed math rendering options and related code from MarkdownRenderer to simplify the rendering process.
- Cleaned up imports in App.vue by removing unused styles for KaTeX and highlight.js.
- Disabled math rendering in the webview about page by removing enableMath option.

Author: BernardXiong

.vscodeignore

@@ -10,9 +10,24 @@ vsc-extension-quickstart.md
 **/*.map
 **/*.ts
 **/.vscode-test.*
-# Exclude all node_modules except marked
+# Exclude all node_modules except markdown-it related packages
 **/node_modules/**
-!node_modules/marked/**
+!node_modules/markdown-it/**
+!node_modules/markdown-it-*/**
+!node_modules/argparse/**
+!node_modules/entities/**
+!node_modules/linkify-it/**
+!node_modules/mdurl/**
+!node_modules/punycode.js/**
+!node_modules/uc.micro/**
+!node_modules/highlight.js/**
+
+# Exclude unnecessary files from included packages to reduce size
+node_modules/highlight.js/**/*.md
+node_modules/highlight.js/styles/**
+node_modules/highlight.js/scss/**
+node_modules/highlight.js/es/**
+node_modules/markdown-it*/**/*.md
 **/.git/**
 **/package-lock.json
 **/.DS_Store