feat: Add user customization and refactor for readability

- Add user customization via automatically detected user.lua file
- Reorganize config options into separate files
- Reorganize plugin loaders into separate files

opts.lua

@@ -0,0 +1,34 @@
+--          ╭─────────────────────────────────────────────────────────╮
+--          │                         CONFIG                          │
+--          ╰─────────────────────────────────────────────────────────╯
+
+local opts = {}
+
+-- Function to merge tables into opts
+local function merge_into_opts(mod)
+	for k, v in pairs(require("config." .. mod)) do
+		opts[k] = v
+	end
+end
+
+-- List of config modules to merge
+local modules = {
+	"colors",
+	"font",
+	"keys",
+	"window",
+	"platform",
+}
+
+-- If USERCONFIG is true, merge userconfig
+if USERCONFIG then
+	merge_into_opts("user")
+end
+
+-- Merge all modules into opts
+for _, mod in ipairs(modules) do
+	merge_into_opts(mod)
+end
+
+-- Return config options
+return opts