Add keccak-lys example EE written in Lys

Author: axic

keccak-lys.yaml

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+beacon_state:
+  execution_scripts:
+    - scripts/keccak-lys/build/main.wasm
+shard_pre_state:
+  exec_env_states:
+    - "0000000000000000000000000000000000000000000000000000000000000000"
+shard_blocks:
+  - env: 0
+    data: ""
+  - env: 0
+    data: ""
+shard_post_state:
+  exec_env_states:
+    - "c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470"
+deposit_receipts: []

scripts/keccak-lys/.gitignore

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+build

scripts/keccak-lys/Makefile

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+all:
+	lys main.lys

scripts/keccak-lys/README.md

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+# keccak-lys
+
+Sample EE script written in [Lys].
+
+## Build
+
+Install Node.js and npm first. Then install the lys compiler:
+```shell
+npm i -g lys
+```
+
+Finally build the EE via:
+```shell
+lys main.lys
+```
+
+Or simply run `make`.
+
+[Lys]: https://github.com/lys-lang/lys

scripts/keccak-lys/eth2.lys

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+#[extern "env" "loadPreStateRoot"]
+fun loadPreStateRoot(ptr: u32): void = panic()
+
+#[extern "env" "eth2_blockDataSize"]
+fun blockDataSize(): u32 = panic()
+
+#[extern "env" "eth2_blockDataCopy"]
+fun blockDataCopy(ptr: u32, offset: u32, len: u32): void = panic()
+
+#[extern "env" "eth2_savePostStateRoot"]
+fun savePostStateRoot(ptr: u32): void = panic()

scripts/keccak-lys/main.lys

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+import system::hash::keccak
+
+import eth2
+
+#[export]
+fun main(): void = {
+   var len = blockDataSize()
+   var input = bytes(len)
+   blockDataCopy(input.ptr, 0 as u32, len)
+
+   var k = Keccak()
+   Keccak.update(k, input)
+   var ret = Keccak.digest(k)
+
+   savePostStateRoot(ret.ptr)
+}