Re-add Neovim configuration files

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

config/neovim/plugin/dial.lua

@@ -0,0 +1,45 @@
+local augend = require "dial.augend"
+local dial_config = require "dial.config"
+
+dial_config.augends:register_group {
+  visual = {
+    augend.integer.alias.decimal,
+    augend.integer.alias.hex,
+    augend.date.alias["%Y/%m/%d"],
+    augend.constant.alias.alpha,
+    augend.constant.alias.Alpha,
+  },
+
+  mygroup = {
+    augend.constant.new {
+      elements = { "TRUE", "FALSE" },
+      word = true,
+      cyclic = true,
+    },
+
+    augend.constant.new {
+      elements = { "public", "protected", "private" },
+      word = true,
+      cyclic = true,
+    },
+
+    augend.constant.new {
+      elements = { "&&", "||" },
+      word = false,
+      cyclic = true,
+    },
+
+    augend.date.alias["%d/%m/%Y"],
+    augend.constant.alias.bool, -- boolean value (true <-> false)
+    augend.integer.alias.decimal,
+    augend.integer.alias.hex,
+    augend.semver.alias.semver,
+  },
+}
+
+local dial_map = require "dial.map"
+
+vim.keymap.set("n", "<C-a>", dial_map.inc_normal "mygroup")
+vim.keymap.set("n", "<C-x>", dial_map.dec_normal "mygroup")
+vim.keymap.set("v", "<C-a>", dial_map.inc_normal "visual")
+vim.keymap.set("v", "<C-x>", dial_map.dec_normal "visual")