book/zkas: Add introductory text.

book/src/SUMMARY.md

@@ -8,4 +8,4 @@
 - [zkas](zkas/zkas.md)
   - [Bincode](zkas/bincode.md)
   - [Examples](zkas/examples.md)
-    - [Sapling payment scheme](zkas/examples/sapling.md)
+    - [Sapling scheme](zkas/examples/sapling.md)

book/src/zkas/zkas.md

@@ -1,5 +0,0 @@
-zkas
-====
-
-zkas is a compiler for the Halo2 zkVM langage used in
-[DarkFi](https://github.com/darkrenaissance/darkfi).

book/src/zkas/zkas.md

@@ -0,0 +1 @@
+../../../zkas/README.md

zkas/README.md

@@ -0,0 +1,18 @@
+zkas
+====
+
+zkas is a compiler for the Halo2 zkVM langage used in
+[DarkFi](https://github.com/darkrenaissance/darkfi).
+
+The documentation on both the compiler and the language can be found
+in the book: https://darkrenaissance.github.io/darkfi/zkas/zkas.html
+
+The current implementation found in the DarkFi repository inside
+https://github.com/darkrenaissance/darkfi/tree/master/zkas is the
+reference compiler and language implementation. It is a toolchain
+consisting of a lexer, parser, static and semantic analyzers, and a
+binary code compiler.
+
+The [`main.rs`](https://github.com/darkrenaissance/darkfi/blob/master/zkas/src/main.rs)
+file shows how this toolchain is put together to produce binary code
+from source code.