Add note on JavaScript libraries

README.md

@@ -63,3 +63,11 @@ Dark mode:
 Book metadata display:
 
 ![About](data/screenshots/about.png)
+
+---
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+**Note:** three JavaScript libraries are bundled in this software:
+
+- [Epub.js](https://github.com/futurepress/epub.js/), which is licensed under [FreeBSD](https://github.com/futurepress/epub.js/blob/master/license). The included file is patched to fix [futurepress/epub.js#942](https://github.com/futurepress/epub.js/issues/942)
+- The minified version of [JSZip](https://stuk.github.io/jszip/), which is dual-licensed. You may use it under the MIT license or the GPLv3 license. See [LICENSE.markdown](https://github.com/Stuk/jszip/blob/master/LICENSE.markdown)
+- A browserified version of [Cheerio](https://cheerio.js.org/), which is licensed under [MIT](https://github.com/cheeriojs/cheerio/blob/master/LICENSE). Cheerio is used to parse and extract data from Wiktionary