add a Containerfile and instructions

Containerfile

@@ -0,0 +1,14 @@
+#
+# Build: podman build -t xword-dl .
+#        podman tag xword-dl:latest xword-dl:$(git describe --tags)
+#
+# Run: podman run --rm --tz local -v $HOME/my-xwords:/xw:Z xword-dl [...]
+#
+FROM docker.io/library/alpine:latest
+WORKDIR /xw
+COPY . /xword-dl
+RUN apk update && \
+    apk add python3 py3-setuptools py3-pip gcc python3-dev musl-dev libxml2 libxslt libxml2-dev libxslt-dev && \
+    python3 -m pip install /xword-dl && \
+    apk del gcc python3-dev musl-dev libxslt-dev libxml2-dev
+ENTRYPOINT ["/usr/bin/xword-dl"]

README.md

@@ -52,6 +52,15 @@ in the downloaded directory may be enough.
 
 But in either case, you probably want to install `xword-dl` and its dependencies in a dedicated virtual environment. I use `virtualenv` and `virtualenvwrapper` personally, but that's a matter of preference. If you're already feeling overwhelmed by the thought of managing Python packages, know you're not alone. The [official documentation is pretty good](https://packaging.python.org/tutorials/installing-packages/), but it's a hard problem, and it's not just you. If it's any consolation, learning how to use virtual environments today on something sort of frivolous like a crossword puzzle downloader will probably save you from serious headaches in the future when the stakes are higher.
 
+Alternatively, if you have the [podman](https://podman.io/) container engine installed, you can build and run `xword-dl` in a container image:
+
+```
+podman build -t xword-dl .      [slow; only needs to be run once per release]
+podman tag xword-dl:latest xword-dl:$(git describe --tags)  [optional]
+...
+podman run --rm --tz local -v $HOME/my-xwords:/xw:Z xword-dl [...]
+```
+
 ## Usage
 
 Once installed, you can invoke `xword-dl`, providing the short code of the site from which to download. If you run `xword-dl` without providing a site keyword, it will print some usage instructions and then exit.

requirements.txt

@@ -7,3 +7,4 @@ Unidecode==1.3.6
 pyyaml==6.0.1
 xmltodict==0.13.0
 lxml==4.9.2
+tzlocal==2.1