Add Webpack and babel for transpiling source code

[amoshydra]

Added webpack build pipeline to

• transpile source code with babel
• create a UMD (Universal Module Definition) output

Hope to resolve:

• 文件是es6写的，打包之后不兼容ie #25, IE下报错 , 提示 缺少 ')' #26, IE 下 无法上传图片 或者 apk 文件 #35, 引入imageResize后显示imports not defined #42

Tested with: https://codesandbox.io/s/vq10k6y42y

Backward compatibility

This PR should be backward compatible with the existing version, developer should not be expected to make any changes when updating to this version. if they are using the module according the to README's instruction.

import {container, ImageExtend, QuillWatch} from 'quill-image-extend-module'

The code below however, will cease to work. I suspect the developers should not import this module using this method anyway.

import container from from 'quill-image-extend-module/container'
import ImageExtend from 'quill-image-extend-module/ImageExtend'
import QuillWatch from 'quill-image-extend-module/QuillWatch'

Note for IE compatibility

Although with this PR. developer will be able to use this module on IE. There is still a bug prevent IE user from uploading image. However, I believe this should be resolved in a separate issue #47

[amoshydra]

中文翻译

---

添加了webpack构建管道

• 使用 babel 转换源代码
• 创建 UMD (Universal Module Definition)

希望解决：＃25，＃26,，＃35，＃42
经测试：https://codesandbox.io/s/vq10k6y42y

向后兼容

此PR应与现有版本向后兼容，如果开发者根据 README 的方法使用，在更新此版本时不需进行任何更改。

import {container, ImageExtend, QuillWatch} from 'quill-image-extend-module'

但是，下面的导入方式将会停止运行。我想开发者也不会使用这方法导入。

import container from from 'quill-image-extend-module/container'
import ImageExtend from 'quill-image-extend-module/ImageExtend'
import QuillWatch from 'quill-image-extend-module/QuillWatch'

IE兼容性

虽然有这个 PR 开发人员将能够在 IE 上导入此模块，仍会有一个错误阻止IE用户上传图片。
我认为这应该在另一个 Issue ＃47 中解决