docs(logger): added newline before code block

Author: Andrew Starostin

content/techniques/logger.md

@@ -165,6 +165,7 @@ class MyService {
 ```
 
 In the default logger `context` is printed in the square brackets, like `NestFactory` in the example below:
+
 ```bash
 [Nest] 19096   - 12/08/2019, 7:12:59 AM   [NestFactory] Starting Nest application...
 ```