Replace links to foundations JS exercises (#30480)

Exercises repo restructured in TheOdinProject/javascript-exercises#597

Author: mao-sz

foundations/javascript_basics/data_types_and_conditionals.md

@@ -42,7 +42,7 @@ To give you a good bit of practice, we have created JavaScript exercises for you
 
 Be sure to follow the order presented here. Read all the directions, watch the terminal, and read all the errors.
 
-1. Follow the [instructions in the README of our `javascript-exercises` repository](https://github.com/TheOdinProject/javascript-exercises#how-to-use-these-exercises) to set up your local environment. Once you have forked the repository, cloned it and installed Jest, review each README file prior to completing the following exercises in order:
+1. Follow the [instructions in the README of our `javascript-exercises` repository](https://github.com/TheOdinProject/javascript-exercises#how-to-use-these-exercises) to set up your local environment. Once you have forked the repository, cloned it and installed Jest, review each README file prior to completing the following exercises in order (which are all in the `foundations/` directory):
     - `01_helloWorld` (This exercise is intentionally very beginner-friendly to ensure that you have everything set up properly!)
     - `02_addNumbers`
     - `03_numberChecker`

foundations/javascript_basics/loops_and_arrays.md

@@ -198,7 +198,7 @@ We will teach you the art of actually writing these tests later in the course. F
    - `Copy and sort array`
    - `Shuffle an array`
    - `Filter unique array members`
-1. Go back to the [JavaScript exercises repository](https://github.com/TheOdinProject/javascript-exercises) that we introduced in the [Data Types and Conditionals](https://www.theodinproject.com/lessons/foundations-data-types-and-conditionals) assignment. Review each README file prior to completing the following exercises in order:
+1. Go back to the [JavaScript exercises repository's `foundations/` directory](https://github.com/TheOdinProject/javascript-exercises/tree/main/foundations) that we introduced in the [Data Types and Conditionals](https://www.theodinproject.com/lessons/foundations-data-types-and-conditionals) assignment. Review each README file prior to completing the following exercises in order:
     - `06_repeatString`
     - `07_reverseString`
     - `08_removeFromArray`

foundations/javascript_basics/object_basics.md

@@ -116,7 +116,7 @@ console.log(dog); // { species: "dog" }
 1. More practice with objects (inside arrays!). Fork and clone Wes Bos' [JavaScript30 repository](https://github.com/wesbos/JavaScript30). To follow along with these two video exercises, you'll want to open the `index-START.html` file.
     - [04 - Array Cardio Day 1](https://www.youtube.com/watch?v=HB1ZC7czKRs)
     - [07 - Array Cardio Day 2](https://www.youtube.com/watch?v=QNmRfyNg1lw)
-1. Go back to the [JavaScript exercises repository](https://github.com/TheOdinProject/javascript-exercises). Review each README file prior to completing the following exercises in order:
+1. Go back to the [JavaScript exercises repository's `foundations/` directory](https://github.com/TheOdinProject/javascript-exercises/tree/main/foundations). Review each README file prior to completing the following exercises in order:
    - `12_calculator`
    - `13_palindromes`
    - `14_fibonacci`