docs: update docs for first-time contributor (#1368)

Author: IndraGunawan

CONTRIBUTING.md

@@ -11,7 +11,7 @@ docker build -t frankenphp-dev -f dev.Dockerfile .
 docker run --cap-add=SYS_PTRACE --security-opt seccomp=unconfined -p 8080:8080 -p 443:443 -p 443:443/udp -v $PWD:/go/src/app -it frankenphp-dev
 ```
 
-The image contains the usual development tools (Go, GDB, Valgrind, Neovim...).  
+The image contains the usual development tools (Go, GDB, Valgrind, Neovim...).
 
 If docker version is lower than 23.0, build is failed by dockerignore [pattern issue](https://github.com/moby/moby/pull/42676). Add directories to `.dockerignore`.
 
@@ -49,10 +49,13 @@ cd testdata/
 ../caddy/frankenphp/frankenphp run
 ```
 
-The server is listening on `127.0.0.1:8080`:
+The server is listening on `127.0.0.1:80`:
+
+> [!NOTE]
+> if you are using Docker, you will have to either bind container port 80 or execute from inside the container
 
 ```console
-curl -vk https://localhost/phpinfo.php
+curl -vk http://127.0.0.1/phpinfo.php
 ```
 
 ## Minimal test server

dev.Dockerfile

@@ -46,7 +46,7 @@ RUN apt-get update && \
 	echo 'set auto-load safe-path /' > /root/.gdbinit && \
 	echo '* soft core unlimited' >> /etc/security/limits.conf \
 	&& \
-	apt-get clean 
+	apt-get clean
 
 WORKDIR /usr/local/src/php
 RUN git clone --branch=PHP-8.4 https://github.com/php/php-src.git . && \
@@ -71,7 +71,9 @@ WORKDIR /usr/local/src/watcher
 RUN git clone https://github.com/e-dant/watcher . && \
 	cmake -S . -B build -DCMAKE_BUILD_TYPE=Release && \
 	cmake --build build/ && \
-	cmake --install build
+	cmake --install build && \
+	cp build/libwatcher-c.so /usr/local/lib/libwatcher-c.so && \
+	ldconfig
 
 WORKDIR /go/src/app
 COPY . .

internal/testserver/main.go

@@ -21,7 +21,7 @@ func main() {
 
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 		req, err := frankenphp.NewRequestWithContext(r)
-		if err == nil {
+		if err != nil {
 			panic(err)
 		}