fix: directive syntax highlighting

[kermanx]

fix #2550.

Before	After

About the regex

(?:(?:(v-[\w-]+)(:)?)|([:\.])|(@)|(#))(?:(?:(\[)([^\]]*)(\]))|([\w-]+))?
                  |                         \
(?:(?:(v-[\w-]+)(:)?)|([:\.])|(@)|(#))   (?:(?:(\[)([^\]]*)(\]))|([\w-]+))?
   v-a                                      <omit>                      Then, modifiers or expression
   v-a:                                     [expr]
   #                                        attr-name
   :
   .
   @

[johnsoncodehk]

This is awesome, thanks!