[e.cash] Modify announcement bar for network upgrade

Summary: Update the text and link and adding a countdown clock to the annoucnement bar for the upcoming network update

Test Plan:
preview the site and check the bar looks good and links to /upgrade.

You could also try running locally and change the ACTIVATION_TIMESTAMP value to Date.now() + 5000 to see how the end timer will go

Reviewers: #bitcoin_abc, Mengerian

Reviewed By: #bitcoin_abc, Mengerian

Subscribers: Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D14627