Fix regression from https://github.com/go-gitea/gitea/pull/23801, where
I forgot that the new module will not throw, so the `catch` handlers
were never triggered and in turn, the WEBP was not converted to PNG.
Externalize clipboard copying to the
[clippie](https://github.com/silverwind/clippie) module which I feel I
can maintain outside this repo for shared benefit with my other
projects.
The module is feature-equivalent to the previous code and has one
improvement where it sets `aria-hidden` on the fallback textarea,
preventing screen readers from picking it up. Also it support `Array` of
`content` as well to copy multiple items at once, in case it's ever
needed.
- Replace all default exports with named exports, except for Vue SFCs
- Remove names from Vue SFCs, they are automatically inferred from the
filename
- Misc whitespace-related tweaks
