patch 8.1.0579: cannot attach properties to text

Problem:    Cannot attach properties to text.
Solution:   First part of adding text properties.
diff --git a/runtime/doc/Makefile b/runtime/doc/Makefile
index e4b2b5b..7dbb2ba 100644
--- a/runtime/doc/Makefile
+++ b/runtime/doc/Makefile
@@ -102,6 +102,7 @@
 	tagsrch.txt \
 	term.txt \
 	terminal.txt \
+	textprop.txt \
 	tips.txt \
 	todo.txt \
 	uganda.txt \
@@ -238,6 +239,7 @@
 	tagsrch.html \
 	term.html \
 	terminal.html \
+	textprop.html \
 	tips.html \
 	todo.html \
 	uganda.html \