refactor: preview window uses Yes/No instead of Ok/Cancel (#344)

NOTE: the `o` and `c` keymaps will continue to work. This only changes
the text labels and adds new keymaps for `y` and `n`.

* chore: replace ok and cancel with yes and no in confirmation window

* chore: allow to configure labels and keymaps for confirmation window

* chore: remove potential duplicate cancel keymaps

* chore: update README and oil.txt

* chore: nowait on confirm mappings and cleanup

* refactor: fully transition to yes/no

* move the config from under the `confirmation` key to the `preview`
  key, which is already in use for customizing the window
* fully default to yes/no, keeping the o/c keybindings for backwards
  compatibility
* make all of the `cancel` keybindings explicit (q, C-c, esc)
* more dynamically choose highlighting of the action labels

* refactor: just use yes/no and abandon configuration

---------

Co-authored-by: Steven Arcangeli <stevearc@stevearc.com>

lua/oil/mutator/preview.lua

@@ -45,11 +45,12 @@ end
 ---@param bufnr integer
 ---@param lines string[]
 local function render_lines(winid, bufnr, lines)
-  util.render_text(
-    bufnr,
-    lines,
-    { v_align = "top", h_align = "left", winid = winid, actions = { "[O]k", "[C]ancel" } }
-  )
+  util.render_text(bufnr, lines, {
+    v_align = "top",
+    h_align = "left",
+    winid = winid,
+    actions = { "[Y]es", "[N]o" },
+  })
 end
 
 ---@param actions oil.Action[]
@@ -165,17 +166,22 @@ M.show = vim.schedule_wrap(function(actions, should_confirm, cb)
       end,
     })
   )
-  for _, cancel_key in ipairs({ "q", "C", "c", "<C-c>", "<Esc>" }) do
+
+  -- We used to use [C]ancel to cancel, so preserve the old keymap
+  local cancel_keys = { "n", "N", "c", "C", "q", "<C-c>", "<Esc>" }
+  for _, cancel_key in ipairs(cancel_keys) do
     vim.keymap.set("n", cancel_key, function()
       cancel()
     end, { buffer = bufnr, nowait = true })
   end
-  vim.keymap.set("n", "O", function()
-    confirm()
-  end, { buffer = bufnr })
-  vim.keymap.set("n", "o", function()
-    confirm()
-  end, { buffer = bufnr })
+
+  -- We used to use [O]k to confirm, so preserve the old keymap
+  local confirm_keys = { "y", "Y", "o", "O" }
+  for _, confirm_key in ipairs(confirm_keys) do
+    vim.keymap.set("n", confirm_key, function()
+      confirm()
+    end, { buffer = bufnr, nowait = true })
+  end
 end)
 
 return M