chore: Update CodeSandbox link in README (#2769)

Co-authored-by: Luffy <lufei@docsifyjs.org>

Author: paulhibbitts

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -33,7 +33,7 @@ body:
       label: Steps to reproduce
       description: |
         A description with steps to reproduce the issue.
-        Provide a link to a public repository or create a reproducible [sandbox](https://codesandbox.io/s/307qqv236):
+        Provide a link to a public repository or create a reproducible [sandbox](https://sandbox.docsifyjs.org/):
       placeholder: |
         1. Step 1
         2. Step 2

README.md

@@ -41,7 +41,7 @@ Docsify turns one or more Markdown files into a Website, with no build process r
 
 Get going fast by using a static web server or GitHub Pages with this ready-to-use [Docsify Template](https://github.com/docsifyjs/docsify-template), review the [quick start tutorial](https://docsify.js.org/#/quickstart) or jump right into a CodeSandbox example site with the button below.
 
-[![Edit 307qqv236](https://codesandbox.io/static/img/play-codesandbox.svg)](https://codesandbox.io/s/307qqv236)
+[![Edit in CodeSandbox](https://codesandbox.io/static/img/play-codesandbox.svg)](https://sandbox.docsifyjs.org/)
 
 ## Showcase