[explorer] Dropdown arrow rotation

Summary:
As suggested adding some roation to the dropdown arrows on the address pages for a better UI
Now when you expand a coins or etoken dropdown the arrow will point up

Test Plan:
preview the site and check an address page with some coins and tokens and try out the dropdowns
here is a an example address /address/ecash:qrk83ygehmy6luflp53hg7yae63cnznt6sd0vvpkfa

Reviewers: #bitcoin_abc, Mengerian

Reviewed By: #bitcoin_abc, Mengerian

Subscribers: Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D16323