fix(utils): add logic for image links

[Nodreame]

Description：

$withBase make 'base' before my img link

Solution

use VuePress Logic：

Result

[antfu]

Probably better to handle here

vitepress/src/client/theme-default/composables/url.ts

Line 6 in 08b9e17

function withBase(path: string): string {

[Nodreame]

Probably better to handle here

vitepress/src/client/theme-default/composables/url.ts

Line 6 in 08b9e17

function withBase(path: string): string {

Thank you for your reply~

I met this problem when I writing Homepage for my post blog. The sample code is shown below：

---
home: true
heroImage: http://img.nodreame.cn/2020-3-23-21-27-49
heroAlt: Logo image
heroText: Hero Title
---

Then I found the template of HomePage and found "$withBase"，so I modify "joinPath" below it.

I read the code for Vitepress to follow your advice, then found that "withBase" was only called by "useNavLink".

Then I added console.log(path) for two files，"withBase" was not called.

So I think its should be handle in "joinPath"，or just in "$withBase".

Looking forward to your reply~ THX~

[yyx990803]

This should've been fixed by #328