docs: add book entry about pnpm patch (#754)

book/src/02_development/07_pnpm_patch.md

@@ -0,0 +1,34 @@
+# `pnpm patch` a dependency
+
+To modify/patch the code of a TypeScript dependency, you can use `pnpm patch`. E.g. to modify the `hardhat` dependency of the `hardhat-tests` folder, run:
+
+```bash
+pnpm patch hardhat@2.22.15
+```
+
+This will output something like:
+
+```bash
+Patch: You can now edit the package at:
+
+  /workspaces/edr/node_modules/.pnpm_patches/hardhat@2.22.15
+
+To commit your changes, run:
+
+  pnpm patch-commit '/workspaces/edr/node_modules/.pnpm_patches/hardhat@2.22.15'
+```
+
+When editing the package, make sure to overwite both the source files in `node_modules/.pnpm_patches/hardhat@2.22.15/src/` and the generated files in `node_modules/.pnpm_patches/hardhat@2.22.15/`.
+
+After you've edited the package at the listed directory and committed it using the `pnpm patch-commit` command, a `hardhat@2.22.15.patch` file will be created in the `patches/` directory. The top-level `package.json` file will also be updated with an entry looking something like this:
+
+```bash
+    "patchedDependencies": {
+      "@defi-wonderland/smock@2.4.0": "patches/@defi-wonderland__smock@2.4.0.patch",
+      "hardhat@2.22.15": "patches/hardhat@2.22.15.patch"
+    }
+```
+
+Each patched dependency has an entry.
+
+> BEWARE: sometimes the automated `pnpm patch-commit` tooling overwrites existing patched dependencies, so make sure that all entries are present.

book/src/SUMMARY.md

@@ -16,6 +16,7 @@
   - [Update N-API targets](02_development/04_update_napi_targets.md)
   - [Using pnpm link](02_development/05_pnpm_link.md)
   - [Style Guide](02_development/06_style_guide.md)
+  - [`pnpm patch` a dependency](02_development/07_pnpm_patch.md)
 
 - [Release](./03_release.md)