docs: improve documentation and add example code

- Add a custom `SkipPathRegexps` function to the README.md file
- Include an example for the custom function in the README.md file
- Add a new file `_example/example04/main.go` with similar content to the README.md file

Signed-off-by: appleboy <[email protected]>

Author: appleboy

README.md

@@ -201,3 +201,56 @@ func main() {
   }
 }
 ```
+
+## Custom `SkipPathRegexps` function
+
+Example for custom `SkipPathRegexps` function
+
+```go
+rxURL := regexp.MustCompile(`^/ping\s*`)
+r.Use(ginzap.GinzapWithConfig(logger, &ginzap.Config{
+  UTC:             true,
+  TimeFormat:      time.RFC3339,
+  SkipPathRegexps: []*regexp.Regexp{rxURL},
+}))
+```
+
+Full example
+
+```go
+package main
+
+import (
+  "fmt"
+  "regexp"
+  "time"
+
+  ginzap "github.com/gin-contrib/zap"
+
+  "github.com/gin-gonic/gin"
+  "go.uber.org/zap"
+)
+
+func main() {
+  r := gin.New()
+
+  logger, _ := zap.NewProduction()
+  rxURL := regexp.MustCompile(`^/ping\s*`)
+
+  r.Use(ginzap.GinzapWithConfig(logger, &ginzap.Config{
+    UTC:             true,
+    TimeFormat:      time.RFC3339,
+    SkipPathRegexps: []*regexp.Regexp{rxURL},
+  }))
+
+  // Example ping request.
+  r.GET("/ping1234", func(c *gin.Context) {
+    c.String(200, "pong "+fmt.Sprint(time.Now().Unix()))
+  })
+
+  // Listen and Server in 0.0.0.0:8080
+  if err := r.Run(":8080"); err != nil {
+    panic(err)
+  }
+}
+```

_example/example04/main.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"fmt"
+	"regexp"
+	"time"
+
+	ginzap "github.com/gin-contrib/zap"
+
+	"github.com/gin-gonic/gin"
+	"go.uber.org/zap"
+)
+
+func main() {
+	r := gin.New()
+
+	logger, _ := zap.NewProduction()
+	rxURL := regexp.MustCompile(`^/ping\s*`)
+
+	r.Use(ginzap.GinzapWithConfig(logger, &ginzap.Config{
+		UTC:             true,
+		TimeFormat:      time.RFC3339,
+		SkipPathRegexps: []*regexp.Regexp{rxURL},
+	}))
+
+	// Example ping request.
+	r.GET("/ping1234", func(c *gin.Context) {
+		c.String(200, "pong "+fmt.Sprint(time.Now().Unix()))
+	})
+
+	// Listen and Server in 0.0.0.0:8080
+	if err := r.Run(":8080"); err != nil {
+		panic(err)
+	}
+}