add fmt module

samples/fmt-test.lua

@@ -0,0 +1,18 @@
+local fmt = require "fmt"
+
+function on_resume()
+    ui:show_lines{
+        fmt.bold("bold"),
+        fmt.italic("italic"),
+        fmt.underline("underline"),
+        fmt.primary("primary"),
+        fmt.secondary("secondary"),
+        fmt.red("red"),
+        fmt.green("green"),
+        fmt.blue("blue"),
+        fmt.colored("lime", "#00FF00"),
+        fmt.bg_colored(fmt.colored("lime background", "#000000"), "#00FF00"),
+        fmt.space().."start with space",
+        fmt.escape("<b>not parsed</b>"),
+    }
+end