Update recover middleware page (#265)

* Add LogErrorFunc in RecoverConfig
* Replace json to yaml in RecoverConfig

Author: lansi951

website/content/middleware/recover.md

@@ -32,26 +32,33 @@ default values for `DisableStackAll` and `DisablePrintStack`.
 ## Configuration
 
 ```go
+// LogErrorFunc defines a function for custom logging in the middleware.
+LogErrorFunc func(c echo.Context, err error, stack []byte) error
+
 RecoverConfig struct {
   // Skipper defines a function to skip middleware.
   Skipper Skipper
 
   // Size of the stack to be printed.
   // Optional. Default value 4KB.
-  StackSize int `json:"stack_size"`
+  StackSize int `yaml:"stack_size"`
 
   // DisableStackAll disables formatting stack traces of all other goroutines
   // into buffer after the trace for the current goroutine.
   // Optional. Default value false.
-  DisableStackAll bool `json:"disable_stack_all"`
+  DisableStackAll bool `yaml:"disable_stack_all"`
 
   // DisablePrintStack disables printing stack trace.
   // Optional. Default value as false.
-  DisablePrintStack bool `json:"disable_print_stack"`
+  DisablePrintStack bool `yaml:"disable_print_stack"`
 
   // LogLevel is log level to printing stack trace.
   // Optional. Default value 0 (Print).
   LogLevel log.Lvl
+
+  // LogErrorFunc defines a function for custom logging in the middleware.
+  // If it's set you don't need to provide LogLevel for config.
+  LogErrorFunc LogErrorFunc
 }
 ```
 
@@ -64,5 +71,6 @@ DefaultRecoverConfig = RecoverConfig{
   DisableStackAll:   false,
   DisablePrintStack: false,
   LogLevel:          0,
+  LogErrorFunc:      nil,
 }
 ```