Update Sidebar styling

[catarak]

The new design is a significant change from the previous version:

More details on Zeplin.

[himanshuc3]

Working on this. Could take some time as my exams are coming through...

[catarak]

all good! this is a pretty in-depth task, maybe it would be good to split it up into smaller ones?

[himanshuc3]

• I've made a PR for this. It's a subset of changes and as said by you, I will split and do it in small commits to manage better rather than lost.

• Also, I would want the icons of files and folders to be placed as right now they are not large enough to be increased in size. I could place icons from flaticon if you want otherwise.

[catarak]

for this project we're using Modern Pictograms for the icons. i can send it to you if you need it!

[himanshuc3]

definitely!

[catarak]

emailed it to you 🎉