Vendor the Shockolate engine and build it via a Docker image with every

dependency (SDL2, SDL2_mixer, fluidsynth-lite, a MIDI soundfont)
prebuilt, so compiling the engine needs no network access - just the
image and the engine source. Add res/assets/extract_assets.sh to pull
the game's data files out of a purchased GOG installer, and a Makefile
that assembles a runnable dist/ from the two.

Also add `make package`, which builds a redistributable tarball that
omits the proprietary game assets (shipping res/GET_ASSETS.txt instead)
plus license information for both the MIT tooling and the GPLv3 engine,
and a Gitea Actions workflow that builds and publishes it to
dl.ladkau.de on every push.

engine/src/Shock Build Notes

@@ -0,0 +1,9 @@
+Shock Build Notes
+----------------
+
+First build the libraries- go into the Libraries folder, and in each sub folder open the project in Metrowerks.  Build the library, then copy the library file you just made into the LIB folder inside the Shock Folder.
+
+Second, build the game- open the Shock project and build it.
+
+You may also have to recompile the precompiled headers in the LIB folder.
+