Fixes build error "The headers or library files could not be found for jpeg, a required dependency when compiling Pillow from source."

.github/test/Dockerfile-alpine

@@ -12,8 +12,10 @@ RUN \
     cargo \
     g++ \
     gcc \
+    jpeg-dev \
     libc-dev \
     libffi-dev \
+    libjpeg \
     libxslt-dev \
     make \
     openssl-dev \