docs: correct article usage in comments (#4301)

- Fix 'an url' to 'a URL' in logger.go comment
- Fix 'an form' to 'a form' in binding/form_mapping.go comment
- Improve grammar consistency in code documentation

binding/form_mapping.go

@@ -175,7 +175,7 @@ func tryToSetValue(value reflect.Value, field reflect.StructField, setter setter
 
 // BindUnmarshaler is the interface used to wrap the UnmarshalParam method.
 type BindUnmarshaler interface {
-	// UnmarshalParam decodes and assigns a value from an form or query param.
+	// UnmarshalParam decodes and assigns a value from a form or query param.
 	UnmarshalParam(param string) error
 }
 

logger.go

@@ -44,7 +44,7 @@ type LoggerConfig struct {
 	// Optional. Default value is gin.DefaultWriter.
 	Output io.Writer
 
-	// SkipPaths is an url path array which logs are not written.
+	// SkipPaths is a URL path array which logs are not written.
 	// Optional.
 	SkipPaths []string