Prettify landing page CSS

[stefanha]

The landing page currently does not fully reflect the UI wireframe in #43. CSS work will be necessary to implement the colors and various details in frontend/coalesce/src/pages/Index.vue.

[kavitakapoor]

To complete this it would be lovely
[] colour all the icons in the Coalesce orange #F35C36
[] have the light background added to #FEF0E5 the non grey sections

After which this can be closed as the rest of the design can't be implemented in the MVP