fix(ItemCardForm): do not slugify whole path

[hendrikheil]

A recent fix in #228 causes any file creation in a folder to be broken.
This might be related to the rename / create issue I am experiencing in #274

This change will perform the slugify call only on the newly entered fullName value of the path, which does not touch the fsPath context. slugify automatically removed the slashes from the whole joined path.

For example, previous to this change:

parentItem.fsPath: 3.pages/
fullName: example file.md
newFsPath: 3.pagesexample-file.md

After:

parentItem.fsPath: 3.pages/
fullName: example file.md
newFsPath: 3.pages/example-file.md

[vercel]

@hendrikheil is attempting to deploy a commit to the Nuxt Team on Vercel.

A member of the Team first needs to authorize it.

[pkg-pr-new]

npm i https://pkg.pr.new/nuxt-content/nuxt-studio@290

commit: 96d92ea

[larbish]

Thanks!