Refactor CSS

[disha1202]

• [x] Remove font family from every where if it is 'Albert Sans', sans-serif as we have defined it globally in app.vue

• [x] There are two :root defined in variable.css file, remove one of them

• [x] Remove all the CSS variables and and only keep those which are being used repeatedly, also improve the name of the CSS variables.

• [x] Remove px from everywhere

[shivamsherje]

few of the changes already done in first PR will reflect after merge