docs: add Hardhat and Foundry links and fix grammar typo

docs/Code4rena-Guidelines.md

@@ -24,7 +24,7 @@ There are a number of known limitations that are explicitly out of scope for the
 - As all consideration items are supplied at the time of order creation, dynamic adjustment of recipients or amounts after creation (e.g. modifications to royalty payout info) is not supported.
 - As all criteria-based items are tied to a particular token, there is no native way to construct orders where items specify cross-token criteria. Additionally, each potential identifier for a particular criteria-based item must have the same amount as any other identifier.
 - As orders that contain items with ascending or descending amounts may not be filled as quickly as a fulfiller would like (e.g. transactions taking longer than expected to be included), there is a risk that fulfillment on those orders will supply a larger item amount, or receive back a smaller item amount, than they intended or expected.
-- As all items on orders supporting partial fills must be "cleanly divisible" when performing a partial fill, orders with multiple items should to be constructed with care. A straightforward heuristic is to start with a "unit" bundle (e.g. 1 NFT item A, 3 NFT item B, and 5 NFT item C for 2 ETH) then applying a multiple to that unit bundle (e.g. 7 of those units results in a partial order for 7 NFT item A, 21 NFT item B, and 35 NFT item C for 14 ETH).
+- As all items on orders supporting partial fills must be "cleanly divisible" when performing a partial fill, orders with multiple items should be constructed with care. A straightforward heuristic is to start with a "unit" bundle (e.g. 1 NFT item A, 3 NFT item B, and 5 NFT item C for 2 ETH) then applying a multiple to that unit bundle (e.g. 7 of those units results in a partial order for 7 NFT item A, 21 NFT item B, and 35 NFT item C for 14 ETH).
 - As Ether cannot be "taken" from an account, any order that contains Ether or other native tokens as an offer item (including "implied" mirror orders) must be supplied by the caller executing the order(s) as msg.value. This also explains why there are no `ERC721_TO_ERC20` and `ERC1155_TO_ERC20` basic order route types, as Ether cannot be taken from the offerer in these cases. One important takeaway from this mechanic is that, technically, anyone can supply Ether on behalf of a given offerer (whereas the offerer themselves must supply all other items). It also means that all Ether must be supplied at the time the order or group of orders is originally called (and the amount available to spend by offer items cannot be increased by an external source during execution as is the case for token balances).
 - As extensions to the consideration array on fulfillment (i.e. "tipping") can be arbitrarily set by the caller, fulfillments where all matched orders have already been signed for or validated can be frontrun on submission, with the frontrunner modifying any tips. Therefore, it is important that orders fulfilled in this manner either leverage "restricted" order types with a zone that enforces appropriate allocation of consideration extensions, or that each offer item is fully spent and each consideration item is appropriately declared on order creation.
 - As orders that have been verified (via a call to `validate`) or partially filled will skip signature validation on subsequent fulfillments, orders that utilize EIP-1271 for verifying orders may end up in an inconsistent state where the original signature is no longer valid but the order is still fulfillable. In these cases, the offerer must explicitly cancel the previously verified order in question if they no longer wish for the order to be fulfillable.
@@ -82,7 +82,7 @@ While wardens should submit any bugs they identify for review, we particularly e
 
 ## **Tests**
 
-A full suite of unit tests using Hardhat and Foundry have been provided in this repo, found in the `test` folder.
+A full suite of unit tests using [Hardhat](https://hardhat.org/) and [Foundry](https://book.getfoundry.sh/) have been provided in this repo, found in the `test` folder.
 
 ## Information: