chore: adjust import order and write down a readme

> Vue Leaflet Next

## Description

This repo contains the WIP to rewrite the vue2-leaflet codebase for vue3 this is High experimental and can be broken at any time, is not actually working as a plugin for now.

The aim is to experiment with various techniques and architectures for vue3.

## Current architecture

- replace mixins with composition API

- use provide/inject instead of `findRealParent`

- simplify simplify and simplify the old codebase

- SSR compatible from the get-go

## What is available now

- a playground page with a working map

- example on how we should build the functions

## Build setup

### [yarn](https://yarnpkg.com) - recommend

```bash

# Install dependencies

yarn install

```

### [npm](https://www.npmjs.com/)

```bash

# Install dependencies

npm install

import { tileLayer } from 'leaflet/dist/leaflet-src.esm';

const { onMounted, ref, computed, inject } = window.Vue;

import { props as layerProps, setup as layerSetup } from '../functions/layer';

import {

  props as gridLayerProps,

  setup as tileLayerSetup

} from '../functions/tileLayer';

const { onMounted, ref, computed, inject } = window.Vue;

export default {

  props: {

    ...layerProps,