chore(test): add sample test project without solhint violations

Author: galargh

packages/hardhat-solhint/test/fixture-projects/no-errors-project/.solhint.json

@@ -0,0 +1,3 @@
+{
+  "extends": "solhint:all"
+}

packages/hardhat-solhint/test/fixture-projects/no-errors-project/contracts/Greeter.sol

@@ -0,0 +1,15 @@
+pragma solidity ^0.8.0;
+
+
+contract Greeter {
+
+    string greeting;
+    constructor(string memory _greeting) public {
+        greeting = _greeting;
+    }
+
+    function greet() public view returns (string memory) {
+        return greeting;
+    }
+
+}

packages/hardhat-solhint/test/fixture-projects/no-errors-project/hardhat.config.js

@@ -0,0 +1,5 @@
+require("../../../src/index");
+
+module.exports = {
+  solidity: "0.5.15",
+};