Fixes for more consistent slugifyTitle (note-filename from link text) behavior

Many bugfixes from foam community.

Fixes:

• fix bug where extension functionality would not work when editing files with language mdx. #51 closes #45
• fix bug where [[Link/Topic]] would not correctly find note namec link-topic.md. tx to @eBerdnA for #52 closes #50
• fix bug where all non-ASCII word characters would be replaced with - characters. tx to @digiguru for #53 closes #47

Diff:

https://github.com/kortina/vscode-markdown-notes/compare/4af718ecf037791507d0d67d59f97ee5b961cccb..43ca88c91653136330c18450fb0ad51698e7decf