doc: format all markdown doc

docs/formatter.md

@@ -1,4 +1,5 @@
 # Formatter
+
 formatter contains some functions for data formatting.
 
 <div STYLE="page-break-after: always;"></div>
@@ -10,6 +11,7 @@ formatter contains some functions for data formatting.
 <div STYLE="page-break-after: always;"></div>
 
 ## Usage:
+
 ```go
 import (
     "github.com/duke-git/lancet/formatter"
@@ -19,15 +21,15 @@ import (
 <div STYLE="page-break-after: always;"></div>
 
 ## Index
-- [Comma](#Comma)
+
+-   [Comma](#Comma)
 
 <div STYLE="page-break-after: always;"></div>
 
 ## Documentation
 
-
-
 ### <span id="Comma">Comma</span>
+
 <p>Add comma to number by every 3 numbers from right. ahead by symbol char.
 Param should be number or numberic string.</p>
 
@@ -36,6 +38,7 @@ Param should be number or numberic string.</p>
 ```go
 func Comma(v interface{}, symbol string) string
 ```
+
 <b>Example:</b>
 
 ```go