refactor!: separate setup config and theme init

When loading plugin spec for other colorschemes they will apply user
options table but will not load the colorscheme when calling the
`require('plugin').setup()` function.

This mirrors that behaviour by separating config initialization and
loading of the colorschemes highlight definitions.

As a result users will be require explicitly call:
`colorscheme vscode` or `require('vscode').load()`

colors/vscode.lua

@@ -1,2 +1,2 @@
 local vscode = require('vscode')
-vscode.setup({})
+vscode.load()

lua/vscode/init.lua

@@ -5,8 +5,12 @@ local vscode = {}
 local config = require('vscode.config')
 local theme = require('vscode.theme')
 
-vscode.setup = function(user_opts)
-    config.setup(user_opts)
+-- Pass setup to config module
+vscode.setup = config.setup
+
+-- Load colorscheme with a given or default style
+---@param style? string
+vscode.load = function()
     vim.cmd('hi clear')
     if vim.fn.exists('syntax_on') then
         vim.cmd('syntax reset')