refactor!: deprecate the "anchor" config option (#106)

This was left over from before we had the "override" function. Now, it
doesn't make much sense to set the anchor as an option because so much
of the rest of the layout logic depends on the anchor being the default.
If a user wants to customize the layout, the override function is the
way to do it.

lua/dressing/config.lua

@@ -16,7 +16,6 @@ local default_config = {
     start_in_insert = true,
 
     -- These are passed to nvim_open_win
-    anchor = "SW",
     border = "rounded",
     -- 'editor' and 'win' will default to being centered
     relative = "cursor",
@@ -120,7 +119,6 @@ local default_config = {
     -- Options for built-in selector
     builtin = {
       -- These are passed to nvim_open_win
-      anchor = "NW",
       border = "rounded",
       -- 'editor' and 'win' will default to being centered
       relative = "editor",
@@ -170,6 +168,13 @@ local M = vim.deepcopy(default_config)
 M.update = function(opts)
   local newconf = vim.tbl_deep_extend("force", default_config, opts or {})
 
+  if newconf.input.anchor or newconf.select.builtin.anchor then
+    vim.notify(
+      "Deprecated: dressing no longer accepts an 'anchor' option. Use the 'override' function to change the anchor",
+      vim.log.levels.WARN
+    )
+  end
+
   for k, v in pairs(newconf) do
     M[k] = v
   end

lua/dressing/input.lua

@@ -229,7 +229,7 @@ local function create_or_update_win(config, prompt, opts)
   else
     winopt = {
       relative = config.relative,
-      anchor = config.anchor,
+      anchor = "SW",
       border = config.border,
       height = 1,
       style = "minimal",

lua/dressing/select/builtin.lua

@@ -76,7 +76,7 @@ M.select = function(config, items, opts, on_choice)
   local col = util.calculate_col(config.relative, width, 0)
   local winopt = {
     relative = config.relative,
-    anchor = config.anchor,
+    anchor = "NW",
     row = row,
     col = col,
     border = config.border,