Chore: update colorscheme

lua/setup/colorscheme.lua

@@ -1,8 +1,8 @@
---local ok, _colors = pcall(require, "melange")
---if not ok then
---    return
---end
+local ok, _ = pcall(require, "onedark")
+if not ok then
+    return
+end
 
 -- setup must be called before loading
 vim.opt.termguicolors = true
-vim.cmd.colorscheme("melange")
+vim.cmd.colorscheme("onedark")