fix minor documentation typos and grammar (#789)

- **StdCheats.sol**: Fix subject–verb agreement in comments describing
Raw structs parsing from JSON.
- **StdChains.sol**: Correct verb form in UX-related comment about
`foundry.toml` alias.
- **StdConfig.sol**: Fix wording of RPC endpoint caching comment for
clarity.

---------

Co-authored-by: zerosnacks <[email protected]>

Author: kilavvy

src/StdChains.sol

@@ -7,7 +7,7 @@ import {VmSafe} from "./Vm.sol";
  * StdChains provides information about EVM compatible chains that can be used in scripts/tests.
  * For each chain, the chain's name, chain ID, and a default RPC URL are provided. Chains are
  * identified by their alias, which is the same as the alias in the `[rpc_endpoints]` section of
- * the `foundry.toml` file. For best UX, ensure the alias in the `foundry.toml` file match the
+ * the `foundry.toml` file. For best UX, ensure the alias in the `foundry.toml` file matches the
  * alias used in this contract, which can be found as the first argument to the
  * `setChainWithDefaultRpcUrl` call in the `initializeStdChains` function.
  *

src/StdCheats.sol

@@ -14,7 +14,7 @@ abstract contract StdCheatsSafe {
     bool private gasMeteringOff;
 
     // Data structures to parse Transaction objects from the broadcast artifact
-    // that conform to EIP1559. The Raw structs is what is parsed from the JSON
+    // that conform to EIP1559. The Raw structs are what are parsed from the JSON
     // and then converted to the one that is used by the user for better UX.
 
     struct RawTx1559 {
@@ -63,7 +63,7 @@ abstract contract StdCheatsSafe {
     }
 
     // Data structures to parse Transaction objects from the broadcast artifact
-    // that DO NOT conform to EIP1559. The Raw structs is what is parsed from the JSON
+    // that DO NOT conform to EIP1559. The Raw structs are what are parsed from the JSON
     // and then converted to the one that is used by the user for better UX.
 
     struct TxLegacy {

src/StdConfig.sol

@@ -103,7 +103,7 @@ contract StdConfig {
             uint256 chainId = resolveChainId(chain_key);
             _chainKeys.push(chain_key);
 
-            // Cache the configure rpc endpoint for that chain.
+            // Cache the configured RPC endpoint for that chain.
             // Falls back to `[rpc_endpoints]`. Panics if no rpc endpoint is configured.
             try vm.parseTomlString(content, string.concat("$.", chain_key, ".endpoint_url")) returns (
                 string memory url