Component for i18n punctuation and spacing

[matthew-white]

The <sentence-separator> component is used when a space character is needed within or between text, but only in some locales. (Currently, Japanese is the only locale for which <sentence-separator> doesn't render a space character.) Historically, we've only used <sentence-separator> for the space between sentences (hence the name), but as of #641, we now use it more expansively for any locale-conditional space character. See #641 (comment). This issue is to rename <sentence-separator> to encompass that broader use. I was thinking of the name <i18n-space>.

[matthew-white]

Hmm I wonder if we should make this component even more expansive. Maybe we should name it <i18n-punc> and have it manage all punctuation/spacing as it relates to i18n. As of #641, we now support i18n commas, and we do something similar on a more ad-hoc basis with parentheses. We could bundle all that together in a single component.

[matthew-white]

This has come up for the entity upload modal (getodk/central#589 and getodk/central#593). The new Pagination component shows ranges of numbers, but different locales write ranges differently. For example, in Japanese, a range looks like 100～200 rather than 100–200. We also have one more comma-separated list in the EntityUploadWarnings component.

I'm taking a different approach from before, making greater use of Intl. For example, we can format a list using Intl.ListFormat, which handles all list-related formatting, including whether there are spaces between text. I like using Intl because it allows us to make fewer assumptions about how the punctuation works, and because it doesn't require translators to translate punctuation. I've created a component <i18n-list>, which parallels Vue I18n's <i18n-n>: just as <i18n-n> uses Intl.NumberFormat.prototype.formatToParts() under the hood, <i18n-list> uses Intl.ListFormat.prototype.formatToParts(). I haven't needed to add a component for ranges yet, just a utility function: the useI18nUtils() composable now returns a formatRange() function.

There may be other punctuation in the future, including punctuation not handled by Intl. That means that we may see more components and/or utility functions in the future. However, given that punctuation so far has been handled specifically rather than generally, I don't think it's likely that we'll want a generic component like <i18n-punc> described above. Also, now that <i18n-list> does some handling of space between text, <sentence-separator> is once again just used for sentence separation. I don't think we need to rename it to <i18n-space>.