1010807: Added custom context menu docs

[BalajiLoganathanSF4826]

Description

Updated custom context menu in React PDF Viewer

• context-menu.md

• custom-context-menu.md

• builtin-context-menu.md

AI Usage:

• Code Studio used in this PR/MR? Yes
  • If Yes:
    • Docs
• Outcome - Saved time
  • Although initially removed a lot of code snippets in documentation, it made work a lot faster by improving the documentation according to diataxis framework

[SyncfusionBuild]

Build Status: INPROGRESS 🔃
Build Location: EJ2-1010807-react-diataxis

[SyncfusionBuild]

CI Status: FAILURE ❌
Source Compilation: SUCCESS ✅
Failure Reason: CI Failure with violation
Build Location: EJ2-1010807-react-diataxis
Technical Error(s): 0
Spelling Error(s): 2
Image Alt Text Error(s): 0
Image Size Error(s): 0
Image Name Error(s): 0
Front matter Error(s): 3
File Path Error(s): 0
CodeSnippet File Path Missing Error(s): 0
Toc Anchor Tags Validation Error(s): 0
MD Tag Validation Error(s): 0

[SyncfusionBuild]

Build Status: INPROGRESS 🔃
Build Location: EJ2-1010807-react-diataxis

[SyncfusionBuild]

CI Status: SUCCESS ✅
Source Compilation: SUCCESS ✅
Build Location: EJ2-1010807-react-diataxis
Technical Error(s): 0
Spelling Error(s): 0
Image Alt Text Error(s): 0
Image Size Error(s): 0
Image Name Error(s): 0
Front matter Error(s): 0
File Path Error(s): 0
CodeSnippet File Path Missing Error(s): 0
Toc Anchor Tags Validation Error(s): 0
MD Tag Validation Error(s): 0