docs: improve theme documentation and migration guide v1 to v2

README.md

@@ -34,7 +34,7 @@ Add plugin at the top list of TPM plugins in `.tmux.conf` and select desired the
 # ~/.tmux.conf
 set -g @plugin 'egel/tmux-gruvbox'
 # set desired options...
-set -g @tmux-gruvbox 'dark' # or 'light'
+set -g @tmux-gruvbox 'dark' # or 'dark256', 'light', 'light256'
 ```
 
 Hit `prefix + I` to fetch the plugin and source it. Your Tmux should be updated with the theme at this point.
@@ -57,24 +57,31 @@ Hit `prefix + I` to fetch the plugin and source it. Your Tmux should be updated
     # ~/.tmux.conf
     run ~/projects/tmux-gruvbox/tmux-gruvbox.tmux
     # set desired options...
-    set -g @tmux-gruvbox 'dark' # or light
+    set -g @tmux-gruvbox 'dark' # or 'dark256', 'light', 'light256'
     ```
 
 ## Configuration options
 
 ### Theme
 
 - default value: `dark256`
-- available themes:
-  - `dark` ([preview][imgur-img-gruvbox-dark-16bit-1x])
-  - `light` ([preview][imgur-img-gruvbox-light-16bit-1x])
-  - `dark256` ([preview][imgur-img-gruvbox-dark256-1x])
-  - `light256` ([preview][imgur-img-gruvbox-light256-1x])
+- available themes
+
+| theme name | color palette | preview link                                  |
+| :--------- | :------------ | :-------------------------------------------- |
+| `dark`     | 16-bit colors | ([preview][imgur-img-gruvbox-dark-16bit-1x])  |
+| `light`    | 16-bit colors | ([preview][imgur-img-gruvbox-light-16bit-1x]) |
+| `dark256`  | 256 color     | ([preview][imgur-img-gruvbox-dark256-1x])     |
+| `light256` | 256 color     | ([preview][imgur-img-gruvbox-light256-1x])    |
 
 ```bash
 set -g @tmux-gruvbox 'dark' # dark256, light, light256
 ```
 
+> [!TIP]
+> Each terminal emulator could behave bit differently with displaying colors.
+> If having
+
 ### Transparent status-bar
 
 - default value: `'false'`