Move Nix files into a nix directory

Move everything from `config` to the root level.

nvim/plugin/terminal.lua

@@ -0,0 +1,25 @@
+local set = vim.opt_local
+
+-- Set local settings for terminal buffers
+vim.api.nvim_create_autocmd("TermOpen", {
+  group = vim.api.nvim_create_augroup("custom-term-open", {}),
+  callback = function()
+    set.number = false
+    set.relativenumber = false
+    set.scrolloff = 0
+
+    vim.bo.filetype = "terminal"
+  end,
+})
+
+-- Easily hit escape in terminal mode.
+vim.keymap.set("t", "<esc><esc>", "<c-\\><c-n>")
+
+-- Open a terminal at the bottom of the screen with a fixed height.
+vim.keymap.set("n", ",st", function()
+  vim.cmd.new()
+  vim.cmd.wincmd "J"
+  vim.api.nvim_win_set_height(0, 12)
+  vim.wo.winfixheight = true
+  vim.cmd.term()
+end)