Add Repositories GUI client screenshots

[andeha]

Changes

Add Repositories — a native macOS Git client
Repositories is a Git client for macOS featuring a visual commit graph, hunk and line-level staging, cherry-pick and squash operations, blame view, Quick Look file preview, and GitHub integration. Built for macOS 13+ with full dark mode support.

Context

Repositories is a native macOS Git client that has been in active development and is now ready to be listed among the GUI clients on git-scm.com. This PR adds the required metadata file and screenshots.

[dscho]

A few things I'd like to clarify before this can move forward.

The PR description says "Built for macOS 13+" but the live website currently says "macOS 26 (Tahoe) or later". Those two claims contradict each other, and the answer matters a lot -- macOS 26 is not even released yet, which would severely limit who can actually use this today.

The app is distributed as a direct DMG download, not through the Mac App Store. I noticed that Streck.ai's other product (Turbine) explicitly advertises being signed and notarized, but the Repositories page makes no such claim. For a proprietary app that handles Git credentials and GitHub PATs, it would be good to know whether it is signed and notarized.

The name "Repositories" is also problematic for the trend_name field. It is an extremely generic English word, so trend_name: "Repositories" will produce completely meaningless Google Trends data -- it will just reflect people searching for the word "repositories" in general, not for this app.

I could not find any reviews, discussions, or third-party mentions of this app anywhere online. The developer background looks fine (established GitHub account, real company with multiple shipped products), so this is not a legitimacy question per se. But some evidence of independent traction would help justify the listing.