Update readme

Author: codeit-ninja

README.md

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 Officially only VTT files are supported by the HTML5 track element. 
 This package will convert your SRT subtitles on the fly to VTT subtitles.
 
+> ✅ This package uses **NO** external dependencies!
+
 ### 👉 What's new in v2?
 - Updated code base to modern JavaScript
 - Added [TextDecoder](https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder?retiredLocale=nl) to support all kinds of encodings