Add Dockerfile and update the README

Dockerfile

@@ -0,0 +1,21 @@
+FROM wiiulegacy/core:0.1
+
+# Get dependencies
+COPY --from=wiiulegacy/dynamic_libs:0.1 /artifacts $DEVKITPRO/portlibs
+COPY --from=wiiulegacy/libutils:0.1 /artifacts $DEVKITPRO/portlibs
+
+# Get latest libgui from git
+RUN git clone https://github.com/Maschell/libgui && cd libgui && git checkout v0.1
+WORKDIR libgui
+
+# install other dependencies
+RUN 7z x -y ./libs/portlibs.zip -o${DEVKITPRO}
+
+RUN make && \
+	find $DEVKITPRO/portlibs -maxdepth 10 -type f -delete && \
+	rm -rf $DEVKITPRO/portlibs/ppc/include && \
+	make install && \
+	7z x -y ./libs/portlibs.zip -o${DEVKITPRO} && \
+	cp -r ${DEVKITPRO}/portlibs /artifacts
+
+WORKDIR /artifacts

README.md

@@ -53,6 +53,14 @@ This package includes:
 - libmad 
 - vorbisidec
 
+# Use the prebuilt files from a Docker image.
+The image `wiiulegacy/libgui` on [Docker Hub](https://hub.docker.com/r/wiiulegacy/libgui/) provides a prebuilt library in the `/artifacts` directory. Copy it into your DevkitPPC portlibs folder.  
+
+Example:  
+```
+COPY --from=wiiulegacy/libgui:0.1 /artifacts $DEVKITPRO/portlibs
+```
+
 # Credits
 - Orignally based on https://github.com/dborth/libwiigui
 - Wii U port / modification / new functions / sound / much more by dimok.