feat: upgrade to Volar 2.1

[johnsoncodehk]

Refs volarjs/volar.js#138, volarjs/services#78

• Volar 2.1 refactors the handling of indentation for embedded code formatting, now controlled by language tools themselves.

• Removed volar.format.initialIndent option, replaced with 3 new options:

  • vue.format.template.initialIndent
  • vue.format.script.initialIndent
  • vue.format.style.initialIndent

• postcss support is now implemented by Vue language tools instead of volar-service-css.

• Volar removes reverseConfigFilePriority and fullCompletionList options, which are no longer supported by the Vue language server.

• Volar removes typescript.tsdk, this option is now redefined by the Vue language server.