[Cashtab] Highlight your own offers in agora orderbook

Summary: For OrderBook components with many offers, the user must click through all of the offers to find their own (if they have some). Modify the css so that offers created by the active wallet are highlighted in a still-subdued-but-recognizably-different color (color is similar to the secondary accent color of the cancel button).

Test Plan:
npm test, see screenshot

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D17453