feat(base): add embark-target face

Embark remaps `vertico-current' to `embark-target' so to make the selected
candidate highlighting consistent it makes sense to align how Doom themes
customises `embark-target', too.

Ref: https://github.com/oantolin/embark/blob/1f6c87d79f5d138cd128c230d727c796b4bc46cd/embark.el#L3333

doom-themes-base.el

@@ -513,6 +513,8 @@
     (elscreen-tab-control-face        :background bg     :foreground bg)
     (elscreen-tab-current-screen-face :background bg-alt :foreground fg)
     (elscreen-tab-other-screen-face   :background bg     :foreground fg-alt)
+    ;;;; embark
+    ((embark-target &inherit vertico-current))
     ;;;; enh-ruby-mode <modes:enh-ruby-mode>
     (enh-ruby-heredoc-delimiter-face :inherit 'font-lock-string-face)
     (enh-ruby-op-face                :foreground operators)