Create master design files for Android

[seanlip]

Platform
Oppia Android

Describe the request
The aim of this issue is to create a set of "master" design files for Web that represent the design team's idea of the ideal Oppia Android app.

When taking on new design projects, designers would then start from these "master" mocks (rather than the actual website), and completed design projects would then be merged back into these mocks. The aim of this is to help the design team maintain a fully-consistent view of the website that is not dependent on whether the dev team has built out certain parts or not.

DESIGN APPROVAL CHECKLIST -- DO NOT EDIT.

• UX Design approved (Android mocks should include dark mode)
• UX Writing approved
• Product approved

For a design project to be completed, it needs approval from UXD, UXW and PM. Please tag the following reviewers when your project is ready (at least one reviewer for each of the bullet points below):

• UXD: @ashley-ya (for Android projects)
• UXW: @ccc253 / @tamiorendain
• PM: @seanlip