Moving between versions should preserve contents of buffer

Since 0.1.0 we've been able to move between different versions of the editor. Hooray!

However, currently the contents of the script buffer (IE the users' code) gets lost between this version migration. In the case that the user entered with a script in the URL we will preserve that script but not any subsequent changes.

I believe the following rule is good:

> Whenever moving between editor versions, put the buffer contents into the URL bar so that the script migrates between versions

Implementation-wise there are a few privacy gotchas - If we put their script in the URL bar then it can/could end up in server logs. If we put it in a cookie we have to mention that we will use cookies in privacy policy.

首先追蹤編輯器版本變更如何處理目前的腳本緩衝區，以及在 URL 中輸入的腳本如何獲得保留。在選擇方案之前，檢視 URL 和 Cookie 的隱私影響；完成的標準是，使用者編輯內容在編輯器版本之間遷移後仍能保留，同時不會留下未解決的上述隱私問題。

由索引模型根據 Issue 內容生成。