build: switch to pyproject

Dockerfile

@@ -1,11 +1,9 @@
 FROM python:3
 
 WORKDIR /usr/src/nhentai
-COPY requirements.txt ./
-RUN pip install --no-cache-dir -r requirements.txt
 
 COPY . .
-RUN pip install .
+RUN pip install --no-cache-dir .
 
 WORKDIR /output
 ENTRYPOINT ["nhentai"]