docs: fix typo (#1858)

Author: Jason-Cooke

README.md

@@ -64,7 +64,7 @@ Install dependencies with:
 npm install
 ```
 
-Optionaly, run the following commands in the project directory to install gulp globally:
+Optionally, run the following commands in the project directory to install gulp globally:
 
 ```lang=bash
 sudo npm install -g gulp