add fish to readme (#181)

Author: skovranek

README.md

@@ -72,6 +72,11 @@ After installing Golang, _open a new shell session_ and run `go version` to make
   source ~/.zshrc
   ```
 
+  ```sh
+  # For fish
+  fish_add_path $HOME/.local/opt/go/bin
+  ```
+
 ### 2. Install the Boot.dev CLI
 
 The following command will download, build, and install the `bootdev` command into your Go toolchain's `bin` directory. Go ahead and run it:
@@ -100,6 +105,11 @@ echo 'export PATH=$PATH:$HOME/go/bin' >> ~/.zshrc
 source ~/.zshrc
 ```
 
+```sh
+# For fish
+fish_add_path $HOME/go/bin
+```
+
 ### 3. Login to the CLI
 
 Run `bootdev login` to authenticate with your Boot.dev account. After authenticating, you're ready to go!