Fix the URL of demo #2

Open
supersonictw wants to merge 2 commits from supersonictw/patch-1 into master

@ -11,7 +11,7 @@ const output = decompress(input);
Available from the npm registry as `bz2`
and from the GitHub registry as `@sheetjs/bz2`.
Try out the [demo](https://http://sheetjs.com/bz2/demo).
Try out the [demo](https://oss.sheetjs.com/bz2).
## API