add strike function to fmt module

lib/fmt.lua

@@ -49,6 +49,10 @@ function fmt.big(str)
     return "<big>"..str.."</big>"
 end
 
+function fmt.strike(str)
+    return "<strike>"..str.."</strike>"
+end
+
 function fmt.space(n)
     local num = 1
 

samples/fmt-test.lua

@@ -14,6 +14,7 @@ function on_resume()
         fmt.bg_colored(fmt.colored("lime background", "#000000"), "#00FF00"),
         fmt.small("small font"),
         fmt.big("big font"),
+        fmt.strike("The crossed out text"),
         fmt.space().."start with space",
         fmt.space(4).."start with tab",
         fmt.escape("<b>not parsed</b>"),