make: add end2end target

Makefile

@@ -48,6 +48,7 @@ help:
 # $(ZIG) commands
 # ------------
 .PHONY: build build-dev run run-release shell test bench download-zig wpt data get-v8 build-v8 build-v8-dev
+.PHONY: end2end
 
 zig_version = $(shell grep 'recommended_zig_version = "' "vendor/zig-js-runtime/build.zig" | cut -d'"' -f2)
 
@@ -94,6 +95,11 @@ wpt-summary:
 test:
 	@TEST_FILTER='${F}' $(ZIG) build test -freference-trace --summary all
 
+## Run demo/runner end to end tests
+end2end:
+	@test -d ../demo
+	cd ../demo && go run runner/main.go
+
 ## v8
 get-v8:
 	@printf "\e[36mGetting v8 source...\e[0m\n"

README.md

@@ -243,6 +243,20 @@ For dev env, use `make build-v8-dev`.
 
 You can test Lightpanda by running `make test`.
 
+### End to end tests
+
+To run end to end tests, you need to clone the [demo
+repository](https://github.com/lightpanda-io/demo) into `../demo` dir.
+
+You have to install the [demo's node
+requirements](https://github.com/lightpanda-io/demo?tab=readme-ov-file#dependencies-1)
+
+You also need to install [Go](https://go.dev) > v1.24.
+
+```
+make end2end
+```
+
 ### Web Platform Tests
 
 Lightpanda is tested against the standardized [Web Platform