fix: decode hash when clicking on same hash to correctly scroll on non ascii hashes

[henrikvilhelmberglund]

This PR adds a missing decodeURIComponent(hash) in the same hash scrolling code to make sure non ascii hashes scroll properly. This exists for normal clicking code but is missing in the same hash code.

I have no idea how to write a test for this but here is code that can be checked in the playground:

Code

<nav>
  <a href="#一">一</a>
  <a href="#2">2</a>
  <a href="#three">three</a>
<a href="#go-to-encöded">Anchor demo (non-ASCII)</a>
<a href="#go-to-.=">Anchor demo (special characters)</a>
  <a href="#4">四</a>
  <a href="#五five">五</a>
</nav>
<div class="scroll-container">
  <div class="scroll-page" id="一"><a href="#一">一</a></div>
  <div class="scroll-page" id="2">2</div>
  <div class="scroll-page" id="three">three</div>
  <div class="scroll-page" id="go-to-encöded">non-ASCII</div>
  <div class="scroll-page" id="go-to-.=">special characters</div>
  <div class="scroll-page" id="4"><a href="#4">四</a></div>
  <div class="scroll-page" id="五five"><a href="#五five">五</a></div>
</div>

<style>
  a {
  	display: inline-block;
  	width: 50px;
  	text-decoration: none;
  }
  nav,
  .scroll-container {
  	display: block;
  	margin: 0 auto;
  	text-align: center;
  }
  nav {
  	width: 339px;
  	padding: 5px;
  	border: 1px solid black;
  }
  .scroll-container {
  	width: 350px;
  	height: 200px;
  	overflow-y: scroll;
  	scroll-behavior: smooth;
  }
  .scroll-page {
  	display: flex;
  	align-items: center;
  	justify-content: center;
  	height: 100px;
  	font-size: 2em;
  }
</style>

Repro:

1. Click 一 in the nav
2. Manually scroll down in the div with the scrollbar
3. Click 一 in the nav again

Result pre PR: doesn't scroll
Result post PR: correctly scrolls to the top

fixes #12684

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Latest commit: 99f2ba6

The changes in this PR will be included in the next version bump.

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@sveltejs/kit	Patch

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[eltigerchino]

Thank you! I've added a test, so if you're curious you can take see what it looks like https://github.com/sveltejs/kit/pull/12699/files#diff-a546a23d82431e7dd623e165253e7a65f2571999354acab18c6f5423b69b9389