Hi, I have read project description and I am familiar with Pipedrive product and familiar with their API's
Also - it won't be a Chrome Extension. Since you want it to embed on Gmail window, it's called Gmail Gadgets and they are easy to integrate in Gmail.
There are two types of Gmail gadgets - Contextual Gadgets and Sidebar Gadgets.
For this project, Contextual Gadgets would be used as we have a context which is Email opened and show data based on person who sent email and fetch his information using Pipe-drive API.
Looking forward to hear from you.
thanks.