Move Nix files into a nix directory

Move everything from `config` to the root level.

nvim/plugin/mini.lua

@@ -0,0 +1,23 @@
+require("mini.ai").setup { n_lines = 500 }
+
+require("mini.align").setup {}
+
+require("mini.bracketed").setup {}
+
+require("mini.hipatterns").setup {
+  highlighters = {
+    note = { pattern = "%f[%w]()NOTE()%f[%W]", group = "MiniHipatternsNote" },
+    todo = { pattern = "%f[%w]()TODO()%f[%W]", group = "MiniHipatternsTodo" },
+  },
+}
+
+require("mini.move").setup {}
+
+require("mini.operators").setup {}
+
+require("mini.statusline").setup {
+  set_vim_settings = false,
+  use_icons = false,
+}
+
+require("mini.surround").setup {}