Added link to separate file about how to reset root password

doc/security/README.md

 # Security
 
-- [Password length limits and How to reset your root password](password_length_limits.md)
+- [Password length limits](password_length_limits.md)
 - [Rack attack](rack_attack.md)
 - [Web Hooks and insecure internal web services](webhooks.md)
-- [Information exclusivity](information_exclusivity.md)
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+- [Information exclusivity](information_exclusivity.md)
+- [Reset your root password] (reset_root_password.md)
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