redis configuration enable include fragments by default

Hello,

lsb_release:
Description: Ubuntu 18.04.5 LTS
Release: 18.04
(but the issue is observed on newer releases too.)

package:
5:4.0.9-1ubuntu0.2 500

Summary:
Expected behaviour: configuration fragments included by default
Current behavior: configuration fragments aren't included by default

Longer form:
Currently the redis.conf configuration file supports the "include" keyword. However, by default, nothing is included. Problems can pop up when local configuration needs to be maintained between upgrades. The upgrade mechanism will prompt for manual intervention with the configuration file, if any changes were made to it. Depending on the amount of customization done therein, this could cause a time-consuming and error-prone situation of having to merge/patch things up.

Other packages, such as Apache and MySQL (for instance, amongst many others), have addressed this by providing a "conf.d"-style directory and having "include conf.d/*" type of statement in the default configuration file that's maintained by the package maintainer. This is effectively the standard approach seen nowadays in Linux.

The benefit is obvious: one can simply drop their local configuration file into the provided conf.d directory and upgrade away with far fewer worries.

In summary, please consider affecting the following two (or three) changes to the redis package:
1) add an empty /etc/redis/conf.d directory to the package

2) add the statement "include /etc/reds/conf.d/*" to the bottom of the official /etc/redis.conf file to serve as an override of all default settings

3) it's not clear to me whether wildcard can actually currently be specified in the include statement. If they currently cannot be specified, please patch the code to glob using the pattern specified in the include, instead of targeting an individual file.

Thank you!