Add working Dockerfile to build the rom

[luisvega23]

Hello ! This PRs adds a Dockerfile that let the user build the ROM from the get-go without installing any package in itsown computer.
To make it work, first build the dockerfile:

cd ${pokefirered-expansion-directory}
docker build -t pokefirered:builder .

Then, run the container:

docker run --it --entrypoint bash --name compiler pokefirered:builder make firered_rev1

Finally, get the created rom from the container

docker cp compiler:/home/pokefirered/pokefirered_rev1.gba . && date