removed article 'a' and added 'the'

Author: Sam Vitare

src/content/0/en/part0b.md

@@ -409,7 +409,7 @@ Let's review what happens when the page <https://studies.cs.helsinki.fi/examplea
 
 - The browser fetches the HTML code defining the content and the structure of the page from the server using an HTTP GET request.
 - Links in the HTML code cause the browser to also fetch the CSS style sheet <i>main.css</i>...
-- ...and a JavaScript code file <i>main.js</i>
+- ...and the JavaScript code file <i>main.js</i>
 - The browser executes the JavaScript code. The code makes an HTTP GET request to the address <https://studies.cs.helsinki.fi/exampleapp/data.json>, which
   returns the notes as JSON data.
 - When the data has been fetched, the browser executes an <i>event handler</i>, which renders the notes to the page using the DOM-API.