Added Crafting Interpreters (#2252)

* Added Crafting Interpreters

* Remove trailing slash

* Added 🚧 emoji to Crafting Interpreters

* put 🚧 somewhere that alphabetizes

the other way this could be done is

* [Crafting Interpreters](http://www.craftinginterpreters.com) - Bob Nystrom (HTML) 🚧

free-programming-books.md

@@ -321,6 +321,7 @@
 * [Compiler Design: Theory, Tools, and Examples, Java Edition](http://elvis.rowan.edu/~bergmann/books/cd/java/) - Seth D. Bergmann
 * [Compiling Scala for the Java Virtual Machine](http://lampwww.epfl.ch/~schinz/thesis-final-A4.pdf) - Michel Schinz (PDF)
 * [Compiling Techniques (1969)](http://www.chilton-computing.org.uk/acl/literature/books/compilingtechniques/overview.htm) - F.R.A. Hopgood, Macdonald
+* [Crafting Interpreters (:construction:)](http://www.craftinginterpreters.com) - Bob Nystrom (HTML)
 * [Implementing Functional Languages: A Tutorial](http://research.microsoft.com/en-us/um/people/simonpj/Papers/pj-lester-book/) - Simon Peyton Jones, David Lester
 * [Let's Build a Compiler](http://www.stack.nl/~marcov/compiler.pdf) (PDF)
 * [Linkers and Loaders](http://www.iecc.com/linker/) - John R. Levine