Add AccessManager guide (#4691)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Eric Lau <ericglau@outlook.com>
Co-authored-by: Zack Reneau-Wedeen <z.reneau.wedeen@gmail.com>

contracts/mocks/docs/access-control/AccessManagedERC20MintBase.sol

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import {AccessManaged} from "../../../access/manager/AccessManaged.sol";
+import {ERC20} from "../../../token/ERC20/ERC20.sol";
+
+contract AccessManagedERC20Mint is ERC20, AccessManaged {
+    constructor(address manager) ERC20("MyToken", "TKN") AccessManaged(manager) {}
+
+    // Minting is restricted according to the manager rules for this function.
+    // The function is identified by its selector: 0x40c10f19.
+    // Calculated with bytes4(keccak256('mint(address,uint256)'))
+    function mint(address to, uint256 amount) public restricted {
+        _mint(to, amount);
+    }
+}