fix(zathura): highlight transparency (#638)

## Description

The `highlight-transparency` config option in Zathura has been
deprecated. Transparency is now controlled using the `highlight-color`
and `highlight-active-color` options, which accept RGBA values.

For more details: https://man.archlinux.org/man/zathurarc.5.en#highlight

## Screenshots

### Before

![image](https://github.com/user-attachments/assets/2a3287db-29d6-4630-8251-d3a1a1c8857f)

### After

![image](https://github.com/user-attachments/assets/90bcc998-f267-466e-aba1-58292f3ccadb)

extras/zathura/tokyonight_day.zathurarc

@@ -23,8 +23,8 @@ set inputbar-bg "#e1e2e7"
 set inputbar-fg "#3760bf"
 set statusbar-bg "#e1e2e7"
 set statusbar-fg "#3760bf"
-set highlight-color "#8c6c3e"
-set highlight-active-color "#587539"
+set highlight-color "rgba(140, 108, 62, 0.5)"
+set highlight-active-color "rgba(88, 117, 57, 0.5)"
 set default-bg "#e1e2e7"
 set default-fg "#3760bf"
 set render-loading true

extras/zathura/tokyonight_moon.zathurarc

@@ -23,8 +23,8 @@ set inputbar-bg "#222436"
 set inputbar-fg "#c8d3f5"
 set statusbar-bg "#222436"
 set statusbar-fg "#c8d3f5"
-set highlight-color "#ffc777"
-set highlight-active-color "#c3e88d"
+set highlight-color "rgba(255, 199, 119, 0.5)"
+set highlight-active-color "rgba(195, 232, 141, 0.5)"
 set default-bg "#222436"
 set default-fg "#c8d3f5"
 set render-loading true

extras/zathura/tokyonight_night.zathurarc

@@ -23,8 +23,8 @@ set inputbar-bg "#1a1b26"
 set inputbar-fg "#c0caf5"
 set statusbar-bg "#1a1b26"
 set statusbar-fg "#c0caf5"
-set highlight-color "#e0af68"
-set highlight-active-color "#9ece6a"
+set highlight-color "rgba(224, 175, 104, 0.5)"
+set highlight-active-color "rgba(158, 206, 106, 0.5)"
 set default-bg "#1a1b26"
 set default-fg "#c0caf5"
 set render-loading true

extras/zathura/tokyonight_storm.zathurarc

@@ -23,8 +23,8 @@ set inputbar-bg "#24283b"
 set inputbar-fg "#c0caf5"
 set statusbar-bg "#24283b"
 set statusbar-fg "#c0caf5"
-set highlight-color "#e0af68"
-set highlight-active-color "#9ece6a"
+set highlight-color "rgba(224, 175, 104, 0.5)"
+set highlight-active-color "rgba(158, 206, 106, 0.5)"
 set default-bg "#24283b"
 set default-fg "#c0caf5"
 set render-loading true