added contract_en.md

Author: tanapl

docs/contract_en.md

@@ -0,0 +1,35 @@
+# Setting Up Contract Development Environment (Until Test Code Execution)
+
+## Installing Necessary Libraries
+
+Install the following two libraries by following their respective instructions. Be aware that `snarkjs` should be installed globally.
+
+1. [circom (a language for writing zero-knowledge proof circuits)](https://docs.circom.io/getting-started/installation/)
+2. [snarkjs (a JavaScript library for computing zero-knowledge proofs)](https://www.npmjs.com/package/snarkjs)
+
+Install NPM:
+
+```shell
+$ cd hardhat
+$ pwd
+~/hardhat
+$ yarn
+```
+
+## Building the Zero-Knowledge Proof Circuit
+
+```
+$ yarn build:circuit
+```
+
+## Setting Up .env
+
+```
+$ cp .env.example .env
+```
+
+## Compilation and Test Execution
+
+```
+$ yarn test
+```