Add mentioning to descriptions that Onyx support is only available in Gplay/Github versions

[undefiened]

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• I have searched for similar issues (both open and closed) and cannot find a duplicate
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Motivation

If one installs Saber from F-Droid on their Onyx Boox, they would experience slow performance and currently there is no clear way to learn (aside from searching through issues) that one should instead install the Google Play version.

Solution

Add mentioning of that to app descriptions in F-droid and Github

Alternatives

No response

Saber version

0.25.2

Device

• Device: Onyx Boox Note 3
• OS: Android

Anything else?

Thank you for the great app, I love it!