fix: decode href before using as query selector

[brc-dd]

fixes #950

[gyhyfj]

Could it work if the h2 title start with special char?
Such as+ -

[brc-dd]

@gyhyfj Is it not working?

[gyhyfj]

It doesn't work well at "vitepress": "^1.0.0-alpha.1".
For example:
The md file is like this:

# Reading
...
... 
## `- + * /`
...
...

If I click toc in .VPDocAsideOutline , on the right side of the web,
the page can't scroll to the right place as usual.
Chrome terminal report :

DOMException: Failed to execute 'querySelector' on 'Document': '#-5' is not a valid selector.
    at c (https://www.gyhyfj.com/assets/app.4bd937d4.js:1:124560)
    at $t (https://www.gyhyfj.com/assets/app.4bd937d4.js:1:12734)
    at qe (https://www.gyhyfj.com/assets/app.4bd937d4.js:1:12813)
    at HTMLAnchorElement.n (https://www.gyhyfj.com/assets/app.4bd937d4.js:1:56875)

[brc-dd]

Hey can you create a seperate issue for this one. It's probably because we cannot auto generate an id from that heading. You can try something like

## `- + * /` {#foo}