fix: typo and some formatting

src/content/documentation/develop/getting-started-with-web-ext.md

@@ -53,7 +53,7 @@ date: 2021-01-27 23:47:23
 
 ## Installation
 
-`web-ext` is a node-based application. You install it with `brew` or the [nodejs](https://nodejs.org/) npm tool.
+`web-ext` is a node-based application. You install it with `brew` or the [NodeJS](https://nodejs.org/) `npm` tool.
 
 Install with `brew` using:
 
@@ -99,7 +99,7 @@ Before you start using `web-ext` locate an example extension to use—if you don
 
 ### Testing out an extension
 
-Test an extension in Firefox by `cd`'ing into your extensions’s root directory and entering:
+Test an extension in Firefox by `cd`'ing into your extension’s root directory and entering:
 
 ```shell
 web-ext run