Merge 099a2e66eb into 2d1bd6bf03

* feat: added book

* fix: book name

* fix: trailing slash

* Update books/free-programming-books-subjects.md

Co-authored-by: Eric Hellman <eric@hellman.net>

---------

Co-authored-by: Eric Hellman <eric@hellman.net>

books/free-programming-books-subjects.md

@@ -868,6 +868,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Crypto 101 - Crypto for everyone](https://www.crypto101.io)
 * [Cryptography](https://en.wikibooks.org/wiki/Cryptography) - Wikibooks (HTML) *(:construction: in process)*
 * [CryptoParty Handbook](https://unglue.it/work/141611/)
+* [Fuzzing Book](https://www.fuzzingbook.org) - Andreas Zeller, Rahul Gopinath, Marcel Böhme, Gordon Fraser, Christian Holler (HTML)
 * [Gray Hat Hacking: The Ethical Hacker's Handbook](https://pages.cs.wisc.edu/~ace/media/gray-hat-hacking.pdf) - Allen Harper, Jonathan Ness, Chris Eagle, Shon Harris, Gideon Lenkey, Terron Williams (PDF)
 * [Handbook of Applied Cryptography](https://cacr.uwaterloo.ca/hac/index.html)
 * [How HTTPS works](https://howhttps.works) - dnsimple
@@ -945,6 +946,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Category Theory for Programmers](https://github.com/hmemcpy/milewski-ctfp-pdf) - Bartosz Milewski (PDF)
 * [Delftse Foundations of Computation](https://textbooks.open.tudelft.nl/textbooks/catalog/book/13) - Stefan Hugtenburgand, Neil Yorke-Smith @ TU Delft Open (PDF)
 * [Homotopy Type Theory: Univalent Foundations of Mathematics](https://homotopytypetheory.org/book/) (PDF)
+* [Introduction to Theoretical Computer Science](https://files.boazbarak.org/introtcs/lnotes_book.pdf) - Boaz Barak (PDF)
 * [Introduction to Theory of Computation](https://cglab.ca/~michiel/TheoryOfComputation/) - Anil Maheshwari, Michiel Smid (PDF)
 * [Models of Computation](https://cs.brown.edu/people/jes/book/) - John E. Savage
 * [Principles of Programming Languages](https://web.archive.org/web/20150418034451/http://www.cs.jhu.edu/~scott/pl/book/dist/) - Scott F. Smith *(:card_file_box: archived)*

more/free-programming-playgrounds.md

@@ -92,9 +92,20 @@
 
 ### <a id="csharp"></a>C\#
 
+* [C# playground](https://codapi.org/csharp) - Codeapi
+* [CodeSandbox](https://codesandbox.io/s/c-z2m9v)
+* [.Net Fiddle](https://dotnetfiddle.net)
 * [OnlineGDB](https://www.onlinegdb.com/online_csharp_compiler)
-* [Programiz - Online Compiler](https://www.programiz.com/csharp-programming/online-compiler/)
+* [Getvm](https://getvm.io/playgrounds/c-sharp-playground)
+* [Jdoodle](https://www.jdoodle.com/compile-c-sharp-online)
+* [myCompiler](https://www.mycompiler.io/online-csharp-compiler)
+* [Onecompiler](https://onecompiler.com/csharp/3wv9zujyk)
+* [OnlineGDB](https://www.onlinegdb.com/online_csharp_compiler)
+* [Programiz - Online Compiler](https://www.programiz.com/csharp-programming/online-compiler)
+* [C# Online Compiler](https://www.scholarhat.com/compiler/csharp) - ScholarHat
+* [SharpLab](https://sharplab.io)
 * [SoloLearn](https://code.sololearn.com/csharp)
+* [C# Online Compiler](https://www.w3schools.com/cs/cs_compiler.php) - W3Schools
 
 
 ### <a id="cpp"></a>C++
@@ -164,7 +175,9 @@
 
 ### Git
 
-* [Git](https://learngitbranching.js.org/?NODEMO)
+* [Visualizing Git](https://git-school.github.io/visualizing-git)
+* [Git-school](https://git-school.github.io/visualizing-git)
+* [Learn Git Branching](https://learngitbranching.js.org/?NODEMO)
 
 
 ### Go
@@ -204,6 +217,7 @@
 
 ### Ionic
 
+* [Codepen](https://codepen.io/ajp8164/pen/zrLQYP)
 * [StackBlitz](https://stackblitz.com/fork/ionic)