Fix wikilink heading action not finding files in sub-directories

[3bnz]

Hey,

I'd like to propose a small fix.

Issue

Consider a vault:

vault
├── foo.md # Contains `[[bar#Does Not Exist]]`
└── sub
    └── bar.md

Currently running the code action on the unresolved wiki-link will create a new bar.md file at the root of the vault (or wherever it's configured) and result in:

vault
├── bar.md # New file was created
├── foo.md
└── sub
    └── bar.md

Fix

Strip the heading part to create a link only reference - then use the same logic as gotodef.rs to find the existing nested file-path.