Add instructions on how to build the emulator

doc/EMULATOR.md

@@ -0,0 +1,18 @@
+# Building on Linux
+
+1. Install the following dependencies with your package manager: *SDL2*, *DjVuLibre*, *HarfBuzz*, *OpenJPEG*, *jpeg*, *jbig2dec*, *zlib*.
+2. Unpack the sources for *MuPDF 1.16.0* and copy the files in `contrib/linux/mupdf` in the same directory.
+3. Apply the patch and build the library (it will appear in `build/release`):
+```sh
+patch -p 1 < linux.patch
+./build-linux.sh
+```
+4. Within *Plato*'s directory, go to `src/wrapper` and build the wrapper (replace `<path_to_mupdf>` with the appropriate path):
+```sh
+CFLAGS="-I<path_to_mupdf>/include" ./build.sh
+```
+5. Copy the libraries generated on steps 3 (`libmupdf.so`) and 4 (`libmupdfwrapper.so`) in the appropriate directory (e.g. `/usr/lib`).
+6. And finally, in *Plato*'s directory: 
+```sh
+cargo run --bin plato-emulator --features emulator
+```