init mdbook

Signed-off-by: xermicus <cyrill@parity.io>

docs/src/SUMMARY.md

@@ -0,0 +1,13 @@
+# Summary
+
+[Introduction](README.md)
+
+- [User guide](./user-guide.md)
+    - [Installation](./installation.md)
+    - [CLI guide](./cli.md)
+    - [Hardhat integration](./hardhat.md)
+- [Architecture](./architecture.md)
+    - [Overview](./overview.md)
+    - [Runtime](./runtime.md)
+    - [Differences from EVM](./differences-evm.md)
+- [Development](./development.md)