[e.cash] Add button component

Summary:
Adding a reusable button component for the site.
The component takes a link, text, color, corner, and glow props and renders the styled button
Im adding the first instance of the button on the homepage top section for the only link that currently exists

Test Plan:
Run the app locally with npm i then npm run dev
See if the white button appears as it should and test the link
Try some other props
try corner="topLeft" or "topRight" or "bottomLeft or "bottomRight"
try color="accent"
The default color value is the primary blue and will happen if no color prop is passed or anything but "accent" or "white" is passed
The button should look good in the stealth theme as well
Then run a preview bot @bot preview-e.cash to test build

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: Mengerian, Fabien, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D13811