Migrate library to vue 3

[eriknygren]

Checking if there's any interest to port this (very useful) library to vue 3.

Basically not much needed to change, we needed to update handler names following the migration guide

So the core changes are:

As well as update the testing and dev environment file to mount to vue 3 using the new mounting API

[eriknygren]

I realised this library is looking quite stale, so if anyone is looking for this in vue 3, I published my updated fork under vue-line-clamp-3 so to install:

npm install --save vue-line-clamp-3

import { createApp } from 'vue';
import lineClamp from 'vue-line-clamp-3'

const app = createApp({});
app.use(lineClamp, {
  // plugin options
})

full repo here