Add mocha, chai, and test for Contribution

package.json

@@ -39,11 +39,13 @@
   },
   "homepage": "https://github.com/67P/kredits-contracts#readme",
   "devDependencies": {
+    "@nomicfoundation/hardhat-chai-matchers": "^1.0.3",
     "@nomiclabs/hardhat-ethers": "^2.0.2",
     "@nomiclabs/hardhat-waffle": "^2.0.1",
     "@openzeppelin/contracts-upgradeable": "^4.3.2",
     "@openzeppelin/hardhat-upgrades": "^1.10.0",
     "async-each-series": "^1.1.0",
+    "chai": "^4.3.6",
     "cli-table": "^0.3.1",
     "colors": "^1.0.3",
     "eslint": "^8.14.0",
@@ -57,6 +59,7 @@
     "hardhat-deploy": "^0.11.4",
     "hardhat-deploy-ethers": "^0.3.0-beta.10",
     "homedir": "^0.6.0",
+    "mocha": "^10.0.0",
     "promptly": "^3.0.3",
     "solhint": "^3.3.7",
     "truffle-hdwallet-provider": "^1.0.17",