added a new solution.

Author: gabrysia694

L-B/0019 findMinAndMaxNumber (L-B)/README.md

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+#0019 findMinAndMaxNumber (L-B)
+
+## Problem
+Given an array of numbers, find the highest and lowest numbers in the array.
+
+## Test Cases
+- let numbers = [5, 3, 8, 2, 9]; // Min: 2, Max: 9
+- let numbers = [4, 10, 18, 2, 3]; // Min: 2, Max: 18
+- let numbers = [0, 100, 8, 21, 39]; // Min: 0, Max: 100
+
+## Solution
+
+```javascript
+let numbers = [5, 3, 8, 2, 9];
+
+let min = numbers[0];
+let max = numbers[0];
+
+for (let i = 0; i < numbers.length; i++) {
+  if (numbers[i] < min) {
+    min = numbers[i];
+  }
+  if (numbers[i] > max) {
+    max = numbers[i];
+  }
+}
+
+console.log(`Min: ${min}, Max: ${max}`);
+```
+
+## How it works
+- We start a `for` loop that iterates over each element of the `numbers` array.
+- Inside the loop, we check if the current element is less than the current value of `min`. If it is, we update `min` to the current element. This way, after the loop has finished executing, `min` will hold the smallest value in the numbers array.
+- We also check if the current element is greater than the current value of `max`. If it is, we update `max` to the current element. This way, after the loop has finished executing, `max` will hold the largest value in the `numbers` array.
+
+
+## References
+- [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for)
+- [Wikipedia](https://en.wikipedia.org/wiki/For_loop)
+- [freeCodeCamp](https://www.freecodecamp.org/news/javascript-loops-explained-for-loop-for/)
+
+
+## Problem Added By
+- [GitHub](https://github.com/gabrysia97) 
+
+## Contributing
+Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.
+
+Please make sure to update tests as appropriate.

L-B/0019 findMinAndMaxNumber (L-B)/findMinAndMaxNumber.js

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+let numbers = [5, 3, 8, 2, 9];
+
+let min = numbers[0];
+let max = numbers[0];
+
+for (let i = 0; i < numbers.length; i++) {
+  if (numbers[i] < min) {
+    min = numbers[i];
+  }
+  if (numbers[i] > max) {
+    max = numbers[i];
+  }
+}
+
+console.log(`Min: ${min}, Max: ${max}`);