feat(wpcarro/emacs): Package theme.el

**TL;DR:**
- Rename `colorscheme.el` to `theme.el` to align with Emacs's nomenclature.
- Prune dependencies:
  - `cl-lib`
  - `>`
  - `prelude`

Change-Id: I15f225671b4096ab08913583b7b464e316c95298
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7412
Tested-by: BuildkiteCI
Reviewed-by: wpcarro <wpcarro@gmail.com>

users/wpcarro/emacs/.emacs.d/wpc/wpc-ui.el

@@ -17,11 +17,13 @@
 (require 'prelude)
 (require 'al)
 (require 'fonts)
-(require 'colorscheme)
+(require 'theme)
 (require 'device)
 (require 'laptop-battery)
 (require 'modeline)
 (require 'general)
+(require 'dash)
+(require '>)
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Configuration
@@ -162,7 +164,16 @@
 ;; during initialization?
 (when (device-laptop?) (laptop-battery-display))
 
-(colorscheme-whitelist-set 'doom-peacock)
+(setq theme-whitelist
+      (->> (custom-available-themes)
+           (list-map #'symbol-name)
+           (list-filter (>-> (s-starts-with? "doom-")))
+           (list-map #'intern)
+           cycle-from-list))
+(setq theme-linum-color-override "da5478")
+(add-hook 'theme-after-change
+          (lambda () (prelude-set-line-number-color "#da5478")))
+(theme-whitelist-set 'doom-flatwhite)
 
 (when window-system
   ;; On OSX, JetBrainsMono is installed as "JetBrains Mono", and I'm