Increased navbar icons size and decreased gap

[bhavikrajpal49]

Fixes #3319

Changes Summary

Changes made in main.css

nav a:visited {
color: inherit;
display: inline-block;
fill: inherit;
margin: 0;
padding: 0 10px; /* Decreased the padding to reduce the gap between icons /
font-size: 1.3em; / Increase the font size to make icons larger */
}

[lewisgoddard]

This also changes the size of the navigation links that are text-based on the left. This issue isn't confirmed, so I wouldn't spend too much time on this.