ci: add Webmin module installation steps and checksums

[rdmark]

added instructions for installing the Webmin module tarball to the release notes that are generated by this workflow

generate sha256sum and sha512sum checksum files for Webmin module tarball just like for the netatalk tarball

[augmentcode]

🤖 Augment PR Summary

Summary: Extends the release GitHub Actions workflow to publish checksum files for the Webmin module tarball alongside the Netatalk source tarball.

Why: Makes it easier for users to verify and install the Webmin module artifact by including installation instructions and matching checksum assets in each GitHub Release.

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[augmentcode]

Review completed. 1 suggestion posted.

Comment augment review to trigger a new review at any time.

[rdmark]

augment review

[augmentcode]

Review completed. 1 suggestion posted.

Comment augment review to trigger a new review at any time.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

🔥 Spectest (AFP 3.4) - Flamegraph (AFP_ASSERT active)

Commit: 0ddf5ac7e7f422edbaffacefc49f364bcdb14fb8
Profiling: On-CPU sampling @ 1009 Hz (prime), DWARF call-graph, x86_64
Build: debugoptimized (-O2 -g -fno-omit-frame-pointer)
Total Runtime: 64s, Netatalk Code-time: 6.4%,
Stacks: 1326, SVG size: 868K

🔥 Open interactive Flamegraph (SVG)

📥 Download from artifacts →

🔝 Top 10 leaf functions

Function	Samples
finish_task_switch.isra.0	362735280
_raw_spin_unlock_irqrestore	210108960
__cp_end	99108000
do_syscall_64	93161520
__syscall_cp_c	35678880
memset_orig	27750240
dircache_process_deferred_chain	23785920
_raw_spin_lock	21803760
idle_worker_has_work	20812680
__raw_callee_save___pv_queued_spin_unlock	20812680