Description of problem:

    Right now, the list of packages that are checked is a static list.

    plugins/needs_restarting.py
    <snip>
    # For which package updates we should recommend a reboot
    # Mostly taken from https://access.redhat.com/solutions/27943
    NEED_REBOOT = ['kernel', 'glibc', 'linux-firmware', 'systemd', 'dbus',
                   'dbus-broker', 'dbus-daemon']
    <snip>

    This results in the need to rebuild each time a new package name is added
    to the list. This feature is requesting that the plugin provide the ability
    to add packages to the needs-restarting plugin via a drop-in.

    Similar to the following:
      # echo “kernel-rt” > /etc/dnf/plugins/needs-restarting.d/kernel-rt.conf


Version-Release number of selected component (if applicable):
    dnf-plugins-core-4.0.8-3.el8.noarch


Steps to Reproduce:
    Add a package to the needs-restarting plugin

Actual results:
    1. Add the package to the static list
    2. Rebuild the package

Expected results:
    1. Add a drop-in to the /etc/dnf/plugins/needs-restarting.d/ directory

Additional info:

    This was discussed in the context of the following bug report.

      1806060 – 'needs-restarting -r' does not show that a reboot is required after updating the RT kernel in RHEL 7.6.
      https://bugzilla.redhat.com/show_bug.cgi?id=1806060

    A related effort to this request would be to also include the 
    "kernel-rt" package as a new drop-in which would ship along with this RFE.