Sidenav: Improve look and feel

[SchoolGuy]

Is your feature request related to a problem? Please describe.

As a user
I want to have a pleasant experience using the sidenav
so that I can navigate the website more intuitively and quickly.

Describe the solution you'd like

There are several issues with the sidenav at the moment:

• The subsection headers don't have spacing with the left border of the screen.
• The icon of the project is missing on the left side of the main sidenav header.
• The icons that are in front of the menu items are not material design ones.
• There is no explicit button to close the sidenav.

Describe alternatives you've considered

None

Additional context

• Material design icons: https://fonts.google.com/icons (we are using the filled variant)
• Sidenav documentation: https://v17.material.angular.io/components/sidenav/overview
• Material Design 2 Sidenav documentation: https://m2.material.io/components/navigation-drawer