feat(blink): use block vs. icon for colors (#5037)

## Description

Replace use of icon for `Color` kind with block characters for
`blink.cmp` autocomplete items to make swatches more usable. This also
makes the `blink.cmp` built-in Tailwind integration better match
`nvim-cmp`.

**Note:** I didn't want to replace the default
`LazyVim.config.icons.kinds.Color` in case it's used by other plugins
(e.g. context), but didn't actually find any real uses, so perhaps that
could be done instead? Figured best to leave those untouched as they can
be more generically used as actual icons, and are not always guaranteed
to have custom highlights applied.

## Related Issue(s)

None.

## Screenshots

### Old

![Screenshot 2024-12-13 at 12 18
47](https://github.com/user-attachments/assets/1e73dac9-728d-47ba-8df1-4445b0143177)

### New

![Screenshot 2024-12-13 at 12 18
13](https://github.com/user-attachments/assets/1ff042f1-eda4-4a1b-afcd-658075666eeb)

## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

lua/lazyvim/plugins/extras/coding/blink.lua

@@ -139,6 +139,9 @@ return {
     opts = function(_, opts)
       opts.appearance = opts.appearance or {}
       opts.appearance.kind_icons = LazyVim.config.icons.kinds
+
+      -- Use block instead of icon for color items to make swatches more usable
+      opts.appearance.kind_icons.Color = "██"
     end,
   },