Add entrypoint to run within Docker

entrypoint.sh

+#!/usr/bin/env bash
+#
+# Entrypoint for the xle Docker image.
+# 
+# - /grammar.lfg contains the grammar
+# - $1 contains the sentence to be parsed (passed as parameter)
+
+# Write xlerc containing instructions to parse
+echo "create-parser /grammar.lfg" > xlerc
+echo "parse { $1 }" >> xlerc
+
+# Start X server in background, wait to ensure it has started properly
+Xvfb :123 &
+sleep 1
+
+# Configure apps to use this X server
+export DISPLAY=:123
+
+# Start XLE, this will automatically load xlerc, wait until it has started and the parse is completed
+xle &
+sleep 3
+
+# Take a screenshot of the entire screen and store it
+import -window root /output/screenshot.png