added dockerfile

[thawn]

Summary

added a dockerfile that enables executing mediawiki-to-gfm via docker.

Motivation

For users like me who don't already have php, composer and pandoc installed (but have access to a machine with docker installed), it will be very useful, to run mediawiki-to-gfm via docker.

Usage

Create a new directory and put filename.xml into the new directory:

mkdir my_wiki
mv filename.xml my_wiki/
cd my_wiki

Now you can convert filename.xml using docker.
Note: do not use the output parameter. The output will always be written into the subdirectory output of the current path. (hence the creation of a new directory). This is necessary, because the docker container does not have access to your filesystem except for the current directory (because of the -v $PWD:/app parameter for docker)

docker run -v $PWD:/app thawn/mediawiki-to-gfm --filename=filename.xml

Note: in Readme.md I did not specify a username for the docker hub. I suggest you use your own account, so that you can push new images when you release new versions. I recommend to use a github workflow to automate that.
In push.sh I already specified the username outofcontrol.

I would also be fine with using my docker account for now, but I cannot promise to release updated versions quickly.

[outofcontrol]

Thank you @thawn

[thawn]

Very welcome @outofcontrol and thanks for merging 😄