参考:
http://siwei.me/blog/posts/ruby-paste-image-from-clipboard-to-blog
哈哈,想要这个功能 很久了,所以人啊,就是懒。今天早上自己动手,一小时搞定了。

js读取剪切板的内容:
function handlePaste(e) {
var clipboardData, pastedData;
// Stop data actually being pasted into div
e.stopPropagation();
e.preventDefault();
// Get pasted data via clipboard API
clipboardData = e.clipboardData || window.clipboardData;
pastedData = clipboardData.getData('Text');
// Do whatever with pasteddata
alert(pastedData);
}
document.getElementById('editableDiv').addEventListener('paste', handlePaste);
2. 修改wym: app/assets/javascripts/wymeditor/prototypes.js.erb
283 let clipboardData = pasteEvent.clipboardData || window.clipboardData;
284 let pastedData = clipboardData.getData('Text');
312 }else if(item.type.match(/text/) && pastedData.match(/^http/) ){
313 console.info("== in else if ")
314 if(window.wym){
315 window.wym.paste("<a href='" + pastedData +" ' target='_blank'>" + pastedData + "</a>", false)
316 }else{
317 alert("window.wym is undefined, refresh and try again")
318 }
319 }
3. 重新编辑assets ,就可以了。