[website] eCash User guide for Satochip hardware wallets

Summary:
ABC blog post based on video in T2245.

Dependencies:

1. Work with Bastien on loading an eCash design on their online store. Let me know once you're comfortable in sharing the video and the card design with the Satochip folks for discussion.
2. Work with Satochip team to update their website to reflect native XEC support

3. Publish video to youtube
4. Update the article with the video link then land this blog post

Test Plan:
bundle exec jekyll serve
read through article

Reviewers: Mengerian, bytesofman, #bitcoin_abc

Reviewed By: Mengerian, #bitcoin_abc

Subscribers: aimal

Differential Revision: https://reviews.bitcoinabc.org/D11467