[Feature request] Improve tag suggestions

[fmartingr]

After finding this bug report (#386), I guess I finally understand how tag suggestions are supposed to work. It looks like Shiori's suggestion shows only one of the possible tags, and only when the text entered does not match the suggestion anymore, another possible tag is shown.

That's not intuitive at all. Usually, when you enter a tag the suggestions show all the tags matching the substring typed so far, with a way to select one of the (possibly multiple) suggested tags, either by navigating with the keyboard or by clicking on it.

Originally posted by @mrex in https://github.com/go-shiori/shiori/issues/386#issuecomment-1263967466