doc: add doc for Pad function

docs/strutil.md

@@ -33,8 +33,9 @@ import (
 -   [UpperKebabCase](#UpperKebabCase)
 -   [LowerFirst](#LowerFirst)
 -   [UpperFirst](#UpperFirst)
--   [PadEnd](#PadEnd)
+-   [Pad](#Pad)
 -   [PadStart](#PadStart)
+-   [PadEnd](#PadEnd)
 -   [Reverse](#Reverse)
 -   [SnakeCase](#SnakeCase)
 -   [UpperSnakeCase](#UpperSnakeCase)
@@ -449,6 +450,51 @@ func main() {
 }
 ```
 
+### <span id="Pad">Pad</span>
+
+<p>Pads string on the left and right side if it's shorter than size.</p>
+
+<b>Signature:</b>
+
+```go
+func Pad(source string, size int, padStr string) string
+```
+
+<b>Example:</b>
+
+```go
+import (
+    "fmt"
+    "github.com/duke-git/lancet/v2/strutil"
+)
+
+func main() {
+    result1 := strutil.Pad("foo", 1, "bar")
+	result2 := strutil.Pad("foo", 2, "bar")
+	result3 := strutil.Pad("foo", 3, "bar")
+	result4 := strutil.Pad("foo", 4, "bar")
+	result5 := strutil.Pad("foo", 5, "bar")
+	result6 := strutil.Pad("foo", 6, "bar")
+	result7 := strutil.Pad("foo", 7, "bar")
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+	fmt.Println(result4)
+	fmt.Println(result5)
+	fmt.Println(result6)
+	fmt.Println(result7)
+	// Output:
+	// foo
+	// foo
+	// foo
+	// foob
+	// bfoob
+	// bfooba
+	// bafooba
+}
+```
+
 ### <span id="PadEnd">PadEnd</span>
 
 <p>Pads string on the right side if it's shorter than size.</p>

docs/strutil_zh-CN.md

@@ -449,6 +449,51 @@ func main() {
 }
 ```
 
+### <span id="Pad">Pad</span>
+
+<p>如果字符串长度短于size，则在左右两侧填充字符串。</p>
+
+<b>函数签名:</b>
+
+```go
+func Pad(source string, size int, padStr string) string
+```
+
+<b>示例:</b>
+
+```go
+import (
+    "fmt"
+    "github.com/duke-git/lancet/v2/strutil"
+)
+
+func main() {
+    result1 := strutil.Pad("foo", 1, "bar")
+	result2 := strutil.Pad("foo", 2, "bar")
+	result3 := strutil.Pad("foo", 3, "bar")
+	result4 := strutil.Pad("foo", 4, "bar")
+	result5 := strutil.Pad("foo", 5, "bar")
+	result6 := strutil.Pad("foo", 6, "bar")
+	result7 := strutil.Pad("foo", 7, "bar")
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+	fmt.Println(result4)
+	fmt.Println(result5)
+	fmt.Println(result6)
+	fmt.Println(result7)
+	// Output:
+	// foo
+	// foo
+	// foo
+	// foob
+	// bfoob
+	// bfooba
+	// bafooba
+}
+```
+
 ### <span id="PadEnd">PadEnd</span>
 
 <p>如果字符串长度短于size，则在右侧填充字符串。</p>

strutil/string_example_test.go

@@ -186,6 +186,33 @@ func ExampleUpperFirst() {
 	// Bar大
 }
 
+func ExamplePad() {
+	result1 := Pad("foo", 1, "bar")
+	result2 := Pad("foo", 2, "bar")
+	result3 := Pad("foo", 3, "bar")
+	result4 := Pad("foo", 4, "bar")
+	result5 := Pad("foo", 5, "bar")
+	result6 := Pad("foo", 6, "bar")
+	result7 := Pad("foo", 7, "bar")
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+	fmt.Println(result4)
+	fmt.Println(result5)
+	fmt.Println(result6)
+	fmt.Println(result7)
+
+	// Output:
+	// foo
+	// foo
+	// foo
+	// foob
+	// bfoob
+	// bfooba
+	// bafooba
+}
+
 func ExamplePadEnd() {
 	result1 := PadEnd("foo", 1, "bar")
 	result2 := PadEnd("foo", 2, "bar")