Adding buttons to pages

[judithweng]

This is a very large PR that essentially styles the 'Home', 'About Us', 'How it Works' and 'Data & Privacy' pages. The specifics are listed below.

1. Fixes Implement new custom button component on the homepage #244 : The previous PRs Create 'How it works' page #234 and Style new home page #226 created the 'How it Works' and 'Home' page. However, these did not contain buttons. In this PR, the buttons are added thanks to Ally's button component Created a button component #243.
2. Fixes About us page #201 : An 'About' page already existed from one of Nora's old PR. This page had most of the contents but did not have the latest design. In this PR, the 'About' page follows the latest Figma design.
3. Fixes Data & Privacy page #203 : A 'Data & Privacy' page was made in this PR following the latest Figma design.

Things missing or to fix:

1. The 'Home' page is still not our official home page, but I think once this PR is approved, then we can immediately make this the home page. To visit this 'Home' page, use http://localhost:3000/home

2. Sometimes when I click 'go back' on my browser, I am unable to see the page (see image below), but it works fine when I reload it. This problem, however, ONLY happens in dev mode (with npm run dev) but not in production mode (npm run preview).

[RobertLRead]

I have lighted tested this. I do not fully understand all of it. I approve it.