[3pt] - Add reservations counter - Student C

[codedit334]

Even if the API gives you the number of reservations you will create a specific function to calculate it.

Make sure that the correct number is displayed on the Reservations pop up.

Respect the following rules:

• Each counter should be implemented as a separate module.
• A counter function should look for specific DOM elements (e.g. for the comments counter it should look for comments) and make the counting based on what is actually displayed on the page.
• A counter function should cover all the edge cases you can think about.