v1.31.2 - Better click captions, and screenshots in the store listings

Fixed

• First-draft captions name the clicked button even when the mouse pointer covers part of its words: the same place is read a moment before the click too, and the fuller reading is used when it holds the shorter one (so Click "Ne". is now Click "Next".).
• A checkbox or option button clicked on its box gets its label from the words to the right of it (Click "Create a desktop shortcut".), instead of "the marked spot".
• Text box borders and the text cursor, which OCR reads as | or I, no longer hide the label of an empty text box (Click next to "Product key"), and the border between two buttons no longer joins their words (Click "Back | Next").

New

• Screenshots of the app in the README and in the Linux software center listing (GNOME Software, KDE Discover), plus a Snap Store button and download and Homebrew badges at the top of the README.
• packaging/screenshots/make_screenshots.sh makes the screenshots again after interface changes: it records a made-up setup wizard with the built-in recorder on a virtual display, so the click rings, blurring, and captions in the pictures are the tool's own.