bpo-33856: Add "help" to the welcome message of IDLE (GH-7755)

Make it the same as when one runs 'python'.
diff --git a/Lib/idlelib/pyshell.py b/Lib/idlelib/pyshell.py
index ddfb56a..6746489 100755
--- a/Lib/idlelib/pyshell.py
+++ b/Lib/idlelib/pyshell.py
@@ -1033,7 +1033,7 @@
         return self.shell_title
 
     COPYRIGHT = \
-          'Type "copyright", "credits" or "license()" for more information.'
+          'Type "help", "copyright", "credits" or "license()" for more information.'
 
     def begin(self):
         self.text.mark_set("iomark", "insert")
diff --git a/Misc/NEWS.d/next/IDLE/2018-06-16-21-54-45.bpo-33856.TH8WHU.rst b/Misc/NEWS.d/next/IDLE/2018-06-16-21-54-45.bpo-33856.TH8WHU.rst
new file mode 100644
index 0000000..058f96e
--- /dev/null
+++ b/Misc/NEWS.d/next/IDLE/2018-06-16-21-54-45.bpo-33856.TH8WHU.rst
@@ -0,0 +1 @@
+Add "help" in the welcome message of IDLE