added local-var trigger of rainbow-mode for theme editing
added local-var trigger of rainbow-mode for theme editing

ninrod/gruvbox-theme,greduan/emacs-theme-gruvbox,ninrod/gruvbox-theme,zzgraph/emacs-theme-gruvbox,greduan/emacs-theme-gruvbox,zzgraph/emacs-theme-gruvbox,greduan/emacs-theme-gruvbox,zzgraph/emacs-theme-gruvbox