Add solutions for part 1

tools/builtInChips/DMux8Way.hdl

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+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: tools/builtIn/DMux8Way.hdl
+
+/**
+ * 8-way demultiplexor.  
+ * {a,b,c,d,e,f,g,h} = {in,0,0,0,0,0,0,0} if sel == 000
+ *                     {0,in,0,0,0,0,0,0} if sel == 001
+ *                     etc.
+ *                     {0,0,0,0,0,0,0,in} if sel == 111
+ */
+
+
+CHIP DMux8Way {
+
+    IN  in, sel[3];
+    OUT a, b, c, d, e, f, g, h;
+
+    BUILTIN DMux8Way;
+}
+