add cheatsheet for blockchain (#12612)

* add cheatsheet for blockchain

add cheatsheet for blockchain

* Remove duplicate entry in Blockchain section

Removed duplicate Blockchain Cheat Sheet entry.

* Fix spelling and format in cheatsheets

Corrected spelling of 'BlockChain' to 'Blockchain' and added hyphens before names in the Blockchain section.

* Remove duplicate Blockchain For Beginners link

Removed duplicate link for 'Blockchain For Beginners'.

* Update author names in blockchain cheat sheets

more/free-programming-cheatsheets.md

@@ -3,6 +3,7 @@
 * [Angular](#angular)
 * [APL](#apl)
 * [Artificial Intelligence](#artificial-intelligence)
+* [Blockchain](#blockchain)
 * [C](#c)
 * [C#](#csharp)
 * [C++](#cpp)
@@ -92,6 +93,13 @@
 * [What is Artificial Intelligence?](https://intelligencereborn.com/ArtificialIntelligence.html) IntelligenceReborn (HTML)
 
 
+### Blockchain
+
+* [101 Blockchain Cheat Sheet, Jargon, Glossary and Terminology](https://pupuweb.com/blockchain-bitcoin-cheat-sheet/) - Alex Lim (HTML)
+* [Blockchain Cheat Sheet](https://intellipaat.com/blog/tutorial/blockchain-tutorial/blockchain-cheat-sheet/) - Arpit (HTML)
+* [Blockchain For Dummies Cheat Sheet](https://www.dummies.com/article/technology/information-technology/data-science/general-data-science/blockchain-dummies-cheat-sheet-237567/) - Tiana Laurence (HTML)
+
+
 ### C
 
 * [C Cheat Sheet](https://www.geeksforgeeks.org/c-cheatsheet/) - GeeksforGeeks