Add timestamp based governor with EIP-6372 and EIP-5805 (#3934)

Co-authored-by: Francisco Giordano <fg@frang.io>
Co-authored-by: Ernesto García <ernestognw@gmail.com>
Co-authored-by: Francisco <frangio.1@gmail.com>

contracts/mocks/token/VotesTimestamp.sol

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../../token/ERC20/extensions/ERC20Votes.sol";
+import "../../token/ERC20/extensions/ERC20VotesComp.sol";
+import "../../token/ERC721/extensions/ERC721Votes.sol";
+
+abstract contract ERC20VotesTimestampMock is ERC20Votes {
+    function clock() public view virtual override returns (uint48) {
+        return SafeCast.toUint48(block.timestamp);
+    }
+
+    // solhint-disable-next-line func-name-mixedcase
+    function CLOCK_MODE() public view virtual override returns (string memory) {
+        return "mode=timestamp";
+    }
+}
+
+abstract contract ERC20VotesCompTimestampMock is ERC20VotesComp {
+    function clock() public view virtual override returns (uint48) {
+        return SafeCast.toUint48(block.timestamp);
+    }
+
+    // solhint-disable-next-line func-name-mixedcase
+    function CLOCK_MODE() public view virtual override returns (string memory) {
+        return "mode=timestamp";
+    }
+}
+
+abstract contract ERC721VotesTimestampMock is ERC721Votes {
+    function clock() public view virtual override returns (uint48) {
+        return SafeCast.toUint48(block.timestamp);
+    }
+
+    // solhint-disable-next-line func-name-mixedcase
+    function CLOCK_MODE() public view virtual override returns (string memory) {
+        return "mode=timestamp";
+    }
+}