[e.cash] Add code block component

Summary: Adding a code block component to be used for showing code snippnets. Replacing the inline styles on the mining page

Test Plan: Preview the site and check the code block at the bottom of /mining looks good

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14697