refactor: add generic grant layout component

[nhsz]

Layout components (like ApplicantsLayout, AboutLayout) should solve the layout we need for each page (including mobile), with the corresponding margins and paddings. Besides the fixed layouts mentioned above, we need a genericGrantsLayout for the recurring grants pages (e.g.: Devcon, Academic Grants, Merge Data Challenge), etc and refactor the other components to make the code cleaner and easier to follow and maintain in the future.

[samajammin]

Noting this came up in discussion of #227

This should have been solved at the MergeDataChallengeLayout level, not in the apply page.

[ap501boii]

Yes