Allow display local image in markdown

[amiyatulu]

Instead of providing a separate folder for images, please provide any relative path for images.

For example,
biology/Snips.md
biology/SNP.jpg
biology/image/snips.jpg

In Snips.md
![snip](SNP.jpg) 
![snip](image/snips.jpg) 

Renders only alt txt but doesn't render image.

It will help for easy backup of notes and can be viewed in code editor like vscode.

[danloh]

Actually, the relative path for local file is supported, but there is an asset protocol bug on Tauri.
refs:

tauri-apps/tauri#6158 ,
tauri-apps/tauri#3725 (comment)

Seemingly, it's due to webkit's bug?

EDIT:
On Windows: need to pin Tauri version on 1.2.1 to support;
On Ubuntu22.04/macOS: no support
open an issue: tauri-apps/tauri#6962