修复之前只能替换一个加号的bug，同时也加上了url encode

Author: qiayue

static/js/chat.js

@@ -55,7 +55,7 @@ function sendMessage() {
 }
 
 function getAnswer(inputValue){
- inputValue = inputValue.replace('+', '{[$add$]}');
+ inputValue = encodeURIComponent(inputValue.replace(/\+/g, '{[$add$]}'));
  const url = "./chat.php?q="+inputValue;
  const eventSource = new EventSource(url);