fix: add sapphire-hardhat explaination

docs/build/hardhat.md

@@ -4,13 +4,6 @@ description: Use Sapphire with hardhat
 
 # Hardhat
 
-:::caution Under Construction
-
-This page is **under construction**. Content may be incomplete or subject to
-change.
-
-:::
-
 Hardhat is a versatile development environment for Ethereum, designed to
 streamline tasks like compiling, testing, and deploying smart contracts. It
 offers a modular toolkit and an intuitive workflow that helps developers focus
@@ -80,5 +73,36 @@ You can use now the standard test accounts to run your hardhat tests:
 npx hardhat test --network sapphire-localnet
 ```
 
+## Hardhat Provider
+
+The `@oasisprotocol/sapphire-hardhat` package provides a custom Hardhat provider
+that enables encrypted transactions when working with Oasis Sapphire. This
+makes it easy to test and run tasks involving confidential smart contracts
+directly within your Hardhat setup.
+
+### Installation
+
+To add the provider to your project, run:
+
+ ```shell npm2yarn
+  npm install -D @oasisprotocol/sapphire-hardhat
+  ```
+
+Next, import it in your `hardhat.config.ts` above the rest of your plugins so
+that the provider gets wrapped before anything else starts to use it.
+
+```js
+// ESM
+import '@oasisprotocol/sapphire-hardhat';
+
+// CommonJS
+require('@oasisprotocol/sapphire-hardhat');
+
+/** All other plugins must go below this one! **/
+```
+
+The Hardhat Ethers provider is now wrapped for Sapphire and will encrypt your
+transactions on use.
+
 [Quickstart]: ../quickstart.mdx
 [Localnet]: https://github.com/oasisprotocol/docs/blob/main/docs/build/tools/localnet.mdx