adding gitui theme and explanation

.config/gitui/theme.ron

@@ -0,0 +1,23 @@
+(
+    selected_tab: Cyan,
+    command_fg: Black,
+    selection_bg: Blue,
+    selection_fg: DarkGray,
+    cmdbar_bg: Blue,
+    cmdbar_extra_lines_bg: Blue,
+    disabled_fg: Gray,
+    diff_line_add: Green,
+    diff_line_delete: Red,
+    diff_file_added: LightGreen,
+    diff_file_removed: LightRed,
+    diff_file_moved: LightMagenta,
+    diff_file_modified: Yellow,
+    commit_hash: Magenta,
+    commit_time: LightCyan,
+    commit_author: Green,
+    danger_fg: Red,
+    push_gauge_bg: Blue,
+    push_gauge_fg: Reset,
+    tag_fg: LightMagenta,
+    branch_fg: LightYellow,
+)

README.md

@@ -189,6 +189,18 @@ These directories/files are installed to your home directory and follow the [XDG
 
   </details>
 
+  <details>
+    <summary><code>gitui</code></summary>
+
+  <blockquote>
+
+  File: [`~/.config/gitui/theme.ron`](.config/gitui/theme.ron)
+
+  This just sets a basic colorscheme for gitui so it's readable with [spacechalk.nvim]-like colors :)
+
+  </blockquote>
+
+  </details>
   <details>
     <summary><code>iterm2</code></summary>