[e.cash] Add H2 component

Summary: Adding h2 componenet. It packages the commonly used h2 with the graphic and subheadline that is used throughout the site into one reusable component that takes a text and subtext prop

Test Plan:
npm run dev
check the component renders correctly
try changing the text for the subtext and text prop
ensure it updates properly
@bot preview-e.cash

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D13856