feat: [SecurityConfig]: Añadidos comentarios a la clase SecurityConfig

src/main/java/com/ujaen/tfg/mangaffinity/config/SecurityConfig.java

 package com.ujaen.tfg.mangaffinity.config;
+
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
 import org.springframework.security.crypto.password.PasswordEncoder;
 
+/**
+ * Clase dedicada a la codificación de contraseñas del login
+ */
 @Configuration
 public class SecurityConfig {
     @Bean