Side navigation scrolling fix and image styling

[Chen Hui Jing]

Describe the bug

1. The left navigation does not scroll when it is longer than the viewport height until the end of the main content is reached.
2. Not a bug but a request to have images have rounded corners and a light border

To Reproduce
Steps to reproduce the behavior:

1. Go to a long page like accounts and transfers. You will not be able to scroll the long navigation until you reach the end of the long page. Sad.
2. Go to any image, right now there is no border nor rounded corners.

Expected behavior

1. You should be able to scroll the navigation independently of the main content
2. Images should have rounded corners and a light border around them

[Chen Hui Jing]

Closed by #385