Wherever possible, I have kept as close to the Vue v2 code as I could,
but I was forced to make typing judgement calls in a few places that
should probably be double-checked.
The only exception to the hands-off approach is in the example app,
which I took the liberty of porting to the Vue v3 composition API since
I'd be touching most of the LOC in it anyway.

Partially for the conciseness, partly because it allows explicit types
in a Vue 3 friendly way

The result doesn't have proper type definitions though, so it's not
"working" per se

This patch fixes rendering bugs with icons using strokes for dot
elements, whereby using a stroke weight larger than the circle radius
caused unexpected clipping. We reverted to using ellipse elements for
all cases.

Follow vuejs/core#2687 for status

This is a result of specifying a Prettier version in devDeps, which uses
a newer version of Prettier with slightly different defaults

This provides the appropriate types with the built package, but
continues to be suboptimal and super non-DRY. I haven't yet found a way
to avoid explicitly declaring every named export, unfortunately.

Note: this tree-shakes, but only mostly due to Webpack 4 struggling with
"double-barrel" structures like we have with `index.ts` and `entry.ts`.
Importing a single icon from Phosphor-Vue is not a full 2.5MB anymore,
but there's still a bunch of unnecessary code included (it *does* seem
to purge the unused templates which is the bulk of the library size).
Webpack 5 apparently handles double-barrels better, so we should see
that problem disappear once vue-cli ships Webpack 5 support and clients
start using it (track vuejs/vue-cli#5611)