For any web app that wants to use https://github.com/greenart7c3/Amber you should be able to re-use the code I've written for it in noStrudel https://github.com/hzrd149/nostrudel/blob/master/src/services/amber-signer.ts
The only catch is you cant sign events without the user iterating with the UI. every signature request must originate from a user clicking a button or something. It has to do with browser security stuff
nostr:nevent1qvzqqqqqqypzqun2rcnpe3j8ge6ws2z789gm8wcnn056wu734n6fmjrgmwrp58q3qqsx2n8qr67luchfa575nwwk2jayj00j75e09k0mgfr8s0q0culya0qnwpxvd