Inconsistant Wikilink Logic

[zcysxy]

When dealing with wikilinks, the logic is different for plain links and piped links. In wikilink.ts, spaces in the plain links are replaced with _s, while spaces in piped links preserve.

I recommend adding a setting for users to choose different slugify modes, like [[Hello World]] refers to Hello World.md, hello-world.md, or hello_world.md. Or just leave the linkText AS IS.