Fix README example's missing import (#661)

* Fix example missing import

* Tab and spaces

Co-authored-by: Bernardo Heynemann <bernardo.heynemann@coinbase.com>

README.md

@@ -586,6 +586,7 @@ package main
 import (
 	"github.com/mgechev/revive/cli"
 	"github.com/mgechev/revive/lint"
+	"github.com/mgechev/revive/revivelib"
 )
 
 func main() {
@@ -621,7 +622,7 @@ func LintMyFile(file string) {
 		true,  // Set exit status
 		2048,  // Max open files
 
-        // Then add as many extra rules as you need
+		// Then add as many extra rules as you need
 		revivelib.NewExtraRule(&myRule{}, lint.RuleConfig{}),
 	)