(WIP) feat(cheatcodes): add doc for cool

src/cheatcodes/cool.md

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+## `cool`
+
+### Signature
+
+```solidity
+function cool(address target) external;
+```
+
+### Description
+
+Unmarks the account `target` as touched and cools off all of the `target`'s storage slots. 
+
+Can be used for gas testing purposes by doing required setup in the function and then resetting the slots before doing a `gasleft()` check.
+
+See related EIPs:
+
+- [EIP-2929: Gas cost increases for state access opcodes](https://eips.ethereum.org/EIPS/eip-2929)
+  - the `COLD_SLOAD_COST` is `2100` gas.
+  - the `COLD_ACCOUNT_ACCESS_COST` is `2600` gas.
+  - the `WARM_STORAGE_READ_COST` is `100` gas.
+- [EIP-2930: Optional access lists](https://eips.ethereum.org/EIPS/eip-2930)
+
+### Examples
+
+```solidity
+contract CoolTest is Test {
+    uint256 public slot0 = 1;
+
+    function testCool() public {
+        // init uints...
+
+        // read slot0 of this contract
+        startGas = gasleft();
+        val = slot0;
+        endGas = gasleft();
+        beforeCoolGas = startGas - endGas; // 2100 gas (COLD_SLOAD_COST)
+
+        // cool off this address
+        vm.cool(address(this));
+
+        startGas = gasleft();
+        val = slot0;
+        endGas = gasleft();
+        afterCoolGas = startGas - endGas; // 2100 gas
+
+        // see that the cost of reading slot0 is the same after vm.cool
+        assertEq(beforeCoolGas, afterCoolGas);
+
+        startGas = gasleft();
+        val = slot0;
+        endGas = gasleft();
+        noCoolGas = startGas - endGas;
+
+        // and back to warm access without using vm.cool
+        assertGt(beforeCoolGas, noCoolGas); // 100 gas (WARM_STORAGE_READ_COST)
+    }
+}
+```
+
+### SEE ALSO
+
+- [`store`](./store.md)
+- [`load`](./load.md)
+
+Forge Standard Library
+
+- [Std Storage](../reference/forge-std/std-storage.md)