Re-add Neovim configuration files

Re-included from https://github.com/opdavies/opdavies.nvim.

config/neovim/plugin/fugitive.lua

@@ -0,0 +1,25 @@
+vim.keymap.set("n", "<leader>gc", "<cmd>Git commit<cr><C-w>K")
+
+-- Open the ":Git" window in its own buffer, not a split.
+vim.keymap.set("n", "<leader>gs", "<cmd>0Git<cr>")
+
+vim.api.nvim_create_autocmd("BufWinEnter", {
+  pattern = "*",
+
+  callback = function()
+    if vim.bo.ft ~= "fugitive" then
+      return
+    end
+
+    local bufnr = vim.api.nvim_get_current_buf()
+    local opts = { buffer = bufnr, remap = false }
+
+    vim.keymap.set("n", "<leader>p", function()
+      vim.cmd.Git "push"
+    end, opts)
+
+    vim.keymap.set("n", "<leader>P", function()
+      vim.cmd.Git { "pull", "--rebase" }
+    end, opts)
+  end,
+})