Add tab-line to theme

[paaguti]

Emacs >=27 has a nice tab-line. Here is a small patch to handle it in the theme

diff --git a/arjen-grey-theme.el b/arjen-grey-theme.el
index ed1adcb..eac4122 100644
--- a/arjen-grey-theme.el
+++ b/arjen-grey-theme.el
@@ -84,6 +84,11 @@
  '(gnus-header-subject ((t (:foreground "#eacc8c" ))))
  '(widget-button ((t (:foreground "#909fab" ))))
  '(gnus-summary-normal-read ((t (:foreground "#909fab"))))
+ ;; tab line emacs >=27
+ '(tab-line ((t (:inherit :box (:line-width 3 :color "#2a2f38")))))
+ '(tab-line-tab ((t (:inherit tab-line))))
+ '(tab-line-tab-current ((t (:inherit tab-line :background "#6a6f78" :box (:line-width 3 :color "#6a6f78")))))
+ '(tab-line-tab-inactive ((t (:foreground "#2a2f38" :background "#4a4f58" :box (:line-width 3 :color"#4a4f58" )))))
  )
 
 (custom-theme-set-variables