Replace `node-diacritics` in slugify function with a custom implementation

[phenomen]

Is your feature request related to a problem? Please describe.

@andrewrk/node-diacritics is a very outdated and unmaintained library. It has multiple major bugs that were never fixed.

Related issues:

• Default match broken for cyrillic/russian because of incorrect diactrics removal kentcdodds/match-sorter#57
• Cyrillic "л" is replaced by Latin "n" in the anchor link vuepress#1815

Describe the solution you'd like

Most issues were fixed in vuepress by @larionov with a custom slugify implementation: vuejs/vuepress#1855

Describe alternatives you've considered

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the docs.
• Read the Contributing Guidelines.
• Check that there isn't already an issue that asks for the same feature to avoid creating a duplicate.

[brc-dd]

Ah, we can directly import the slugify function from @mdit-vue/shared, it has the VuePress one.