feat: add well-know path for msid associated

.env.example

@@ -1,2 +1,4 @@
 SERVER_PB="http://localhost:8090"
 PUBLIC_CLIENT_PB="http://127.0.0.1:8090"
+PUBLIC_MSID_ASSOCIATION="{}"
+PUBLIC_PLAUSIBLE_DOMAIN="plausible.example.com"

src/routes/.well-known/microsoft-identity-association.json/+server.js

@@ -0,0 +1,10 @@
+import { MSID_ASSOCIATION } from '$env/static/private';
+
+export async function GET() {
+	return new Response(JSON.stringify(MSID_ASSOCIATION), {
+		headers: {
+			'Cache-Control': `public, max-age=${86400}`,
+			'Content-Type': 'application/json'
+		}
+	});
+}