fix(extension): declare a browser target so plasmo build resolves entries

Parcel reads package.json engines and, seeing only engines.node, built the
extension for a node target instead of the browser target plasmo passes as
its default, which failed with "Failed to resolve '../../popup.tsx'".
Declaring engines.browsers restores plasmo's intended chrome-mv3 target.

Fixes #506

surfsense_browser_extension/package.json

@@ -5,6 +5,9 @@
 	"description": "Extension to collect Browsing History for SurfSense.",
 	"author": "https://github.com/MODSetter",
 	"engines": {
+		"browsers": [
+			"last 1 Chrome version"
+		],
 		"node": ">=18.0.0 <23.0.0",
 		"pnpm": ">=8.0.0"
 	},