banner: add page (#2440)

pages/common/banner.md

@@ -0,0 +1,15 @@
+# banner
+
+> Print the given argument as a large ASCII art.
+
+- Print the text message as a large banner (quotes are optional):
+
+`banner {{"Hello World"}}`
+
+- Print the text message as a banner with a width of 50 characters:
+
+`banner -w {{50}} {{"Hello World"}}`
+
+- Read text from stdin:
+
+`banner`