fix: grammar in StdChains.sol and StdConfig.sol (#784)

Author: kilavvy

src/StdChains.sol

@@ -58,9 +58,9 @@ abstract contract StdChains {
 
     // Maps from the chain's alias (matching the alias in the `foundry.toml` file) to chain data.
     mapping(string => Chain) private chains;
-    // Maps from the chain's alias to it's default RPC URL.
+    // Maps from the chain's alias to its default RPC URL.
     mapping(string => string) private defaultRpcUrls;
-    // Maps from a chain ID to it's alias.
+    // Maps from a chain ID to its alias.
     mapping(uint256 => string) private idToAlias;
 
     bool private fallbackToDefaultRpcUrls = true;

src/StdConfig.sol

@@ -4,7 +4,7 @@ pragma solidity ^0.8.13;
 import {VmSafe} from "./Vm.sol";
 import {Variable, Type, TypeKind, LibVariable} from "./LibVariable.sol";
 
-/// @notice  A contract that parses a toml configuration file and load its
+/// @notice  A contract that parses a toml configuration file and loads its
 ///          variables into storage, automatically casting them, on deployment.
 ///
 /// @dev     This contract assumes a toml structure where top-level keys