Add Dockerfile and instructions to run with docker

.gitignore

@@ -4,3 +4,5 @@ venv
 .coverage
 .garmin-cookies.txt
 coverage.xml
+.env
+.env.*

Dockerfile

@@ -0,0 +1,8 @@
+FROM python:3
+ADD ./ /app
+WORKDIR /app
+RUN pip install -r requirements.txt
+VOLUME /data
+ENV USERNAME example
+ENV PASSWORD examplePassword
+ENTRYPOINT ["python", "-m", "garminworkouts", "--cookie-jar", "/data/.garmin-cookies.txt"] 

README.md

@@ -217,3 +217,30 @@ Note: the date format is as follows : 2021-12-31
 ```shell
 python -m garminworkouts -u [GARMIN_USERNAME] -p [GARMIN_PASSWORD] schedule -d [DATE] -w [WORKOUT_ID]
 ```
+
+## Username and password from environment variables
+
+Alternatively to the `-u` and `-p` arguments, it is possible to load the username and password from the `GARMIN_USERNAME` and `GARMIN_PASSWORD` environment variables:
+
+```shell
+export GARMIN_USERNAME=username
+export GARMIN_PASSWORD=password
+python -m garminworkouts list
+```
+
+# Usage with Docker
+
+```shell
+# store your credentials in a .env file
+cat <<EOT >> .env
+[email protected]
+GARMIN_PASSWORD=mypassword
+EOT
+# name the image
+IMAGE=garminworkouts
+# build the image
+docker build --load -t ${IMAGE} .
+# run the image (the "-v /tmp/garmin:/data" part is optional
+# and will be used to persist the cookies file)
+docker run --env-file=./.env -v /tmp/garmin:/data -ti ${IMAGE} [your command and arguments: list, export, etc.]
+```