QuickGrid: simplify localizing pagination

**Update:** It's all covered except for localization of pagination. It's already possible to do that today by creating a custom paginator (and only 10 or so lines of code) but that's still harder than people would ideally want.

---

### High priority

- [x] On iOS Safari, column options can't be dismissed by tapping on the background. Try listening to `touchstart` (or similar) as well as `click` events.
- [x] On iOS Safari, the sort indicators don't display at all because they use an unsupported unicode character. Try replacing these with SVG images.
- [x] Default sort order is only applied if the data source is loaded asynchronously

### Lower priority

- [x] On iOS Safari, the pagination buttons don't look great because the unicode characters aren't exactly aligned with each other. Try replacing these with SVG images.
- [x] On iOS Safari, there's no way to resize columns. Consider applying support for all the touch events for dragging.
- [ ] No built-in localization of the built-in strings ("Next page" in `alt` text, "14 items", etc.). Developers wanting to customize this have to override the pagination output.
- [ ] The built-in English text for pagination summary doesn't pluralize correctly ("1 items")

Start by locating QuickGrid’s built-in pagination output and the strings described in the issue, then compare it with the custom paginator path. Done means built-in pagination text can be localized and the pagination summary uses correct singular and plural wording.

Written by the indexing model from the issue text.