Update 'README.md'

README.md

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 ## Resources
 - [zlib](https://singlelogin.re/)
+- [Kindle Digital Library](- [Kindle Digital Library](https://www.amazon.co.jp/hz/mycd/digital-console/contentlist/booksAll/dateDsc?pageNumber=1)
 
 #### Reading Stack
 - [Marx, Engels and the Abolition of the Family](https://www.csustan.edu/sites/default/files/History/Faculty/Weikart/Marx-Engels-and-the-Abolition-of-the-Family.pdf) *(added 5/3/2023)*