New package: postman-8.5.1

[Emru1]

General

• This is a new package and it conforms to the quality requirements

Have the results of the proposed changes been tested?

• I use the packages affected by the proposed changes on a regular basis and confirm this PR works for me
• I generally don't use the affected packages but briefly tested this PR

Postman package, based on slack-desktop package, also using desktop entry from #12168

[github-actions]

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