Add Governor contracts (#2672)

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

contracts/governance/extensions/GovernorVotesComp.sol

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../Governor.sol";
+import "../../token/ERC20/extensions/ERC20VotesComp.sol";
+
+/**
+ * @dev Extension of {Governor} for voting weight extraction from a Comp token.
+ *
+ * _Available since v4.3._
+ */
+abstract contract GovernorVotesComp is Governor {
+    ERC20VotesComp public immutable token;
+
+    constructor(ERC20VotesComp token_) {
+        token = token_;
+    }
+
+    /**
+     * Read the voting weight from the token's built in snapshot mechanism (see {IGovernor-getVotes}).
+     */
+    function getVotes(address account, uint256 blockNumber) public view virtual override returns (uint256) {
+        return token.getPriorVotes(account, blockNumber);
+    }
+}