feat: Add multi-modal chat support (file uploads + voice input)

[Isaccseven]

Summary

Adds file upload and voice-to-text input capabilities to the embedded chat widget, addressing #27.

File Upload

• Paperclip button opens native file picker (hidden when file_upload prop is false)
• Selected files show as previews above the input area (image thumbnails or file icon + name)
• Files uploaded to Langflow server via POST /api/v1/files/upload/{flow_id} on send
• File paths included in tweaks object targeting the file_component prop
• Multiple files supported; sequential upload with error handling
• Upload failure shows error message and prevents message send

Voice Input

• Microphone button activates browser's Web Speech API (SpeechRecognition)
• Button automatically hidden in browsers without support (Firefox)
• Transcribed text appended to input field for review before sending
• Pulsing red animation during active recording
• Optional voice_language prop for BCP 47 language code

New Props

Prop	Type	Default	Description
file_upload	boolean	false	Enable file attachment button
file_component	string	-	Flow component ID that accepts files
voice_input	boolean	false	Enable voice-to-text button
voice_language	string	Browser default	Speech recognition language

Files Changed

• src/index.tsx — New prop registrations
• src/chatWidget/index.tsx — Pass props + new CSS classes
• src/chatWidget/chatWindow/index.tsx — File picker, voice input, upload integration
• src/controllers/uploadFiles.ts — New file upload controller
• src/types/chatWidget/index.ts — FileAttachment type
• README.md — Document new props

Testing

• Build compiles successfully (npm run build:react + npm run build:bundle)
• Both features default to false — existing behavior unchanged
• File upload: set file_upload="true" and file_component="<your-component-id>"
• Voice input: set voice_input="true" (test in Chrome/Edge)

Closes #27

[Isaccseven]

Ready for review.