added description file for envelope elements for MM engine

diff --git a/docs/elements/mm_envelope.txt b/docs/elements/mm_envelope.txt
new file mode 100644 (file)
index 0000000..041804f
--- /dev/null
+++ b/docs/elements/mm_envelope.txt
@@ -0,0 +1,2 @@
+Envelopes can be configured to contain a text message for the player.
+All envelopes of the same color contain the same message.