docs: add troubleshooting for yarn installation

README.md

@@ -41,6 +41,38 @@ app locally. Do this like so:
     cd yari
     yarn install
 
+<details>
+  <summary>Troubleshooting installation</summary>
+
+If you get errors while installing dependencies via yarn on a Mac, you may need
+to install some additional packages:
+
+1. First, install [brew](https://brew.sh/) if you haven’t already
+
+1. To fix problems with `gifsicle`:
+
+   ```shell
+   brew install automake autoconf libtool
+   ```
+
+1. To fix problems with `pngquant-bin`:
+
+   ```shell
+   brew install pkg-config
+   ```
+
+1. To fix problems with `mozjpeg`:
+
+   ```shell
+   brew install libpng
+   sudo ln -s /opt/homebrew/Cellar/libpng/1.6.40/lib/libpng16.a /usr/local/lib/libpng16.a
+   ```
+
+You may need to adjust the path to `libpng16.a` depending on the version of
+libpng you have installed.
+
+</details>
+
 Now copy the `.env-dist` file to `.env`:
 
     cp .env-dist .env