add license to package info.rkt file

related to racket/racket#3760

Author: LiberalArtist

simple-tree-text-markup-doc/info.rkt

@@ -18,3 +18,5 @@
 
 (define pkg-authors '(sperber))
 
+(define license
+  '(Apache-2.0 OR MIT))

simple-tree-text-markup-lib/info.rkt

@@ -10,3 +10,6 @@
 (define pkg-authors '(sperber))
 
 (define version "1.1")
+
+(define license
+  '(Apache-2.0 OR MIT))

simple-tree-text-markup-test/info.rkt

@@ -10,3 +10,6 @@
 (define pkg-desc "tests for \"simple-tree-text-markup\"")
 
 (define pkg-authors '(sperber))
+
+(define license
+  '(Apache-2.0 OR MIT))

simple-tree-text-markup/info.rkt

@@ -10,3 +10,6 @@
 (define pkg-desc "Combinator library for simple markup, mainly for displaying messages in a REPL")
 
 (define pkg-authors '(sperber))
+
+(define license
+  '(Apache-2.0 OR MIT))