screenshot-window-sizer: Add additional size

1000x700 is the maximum recommended screenshot size on flathub[0]. As
that's a primary use case of the extension, it makes sense to include
the size.

[0] https://docs.flathub.org/docs/for-app-authors/metainfo-guidelines/quality-guidelines/#reasonable-window-size

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/317>

extensions/screenshot-window-sizer/extension.js

@@ -24,6 +24,7 @@ export default class ScreenshotWindowSizerExtension extends Extension {
         [624, 351],
         [800, 450],
         [1024, 576],
+        [1000, 700],
         [1200, 675],
         [1600, 900],
         [360, 654], // Phone portrait maximized