Migrate Neovim config to 0.12

lua/plugins/filetree.lua

@@ -1,6 +1,6 @@
 local function my_on_attach(bufnr)
   local api = require('nvim-tree.api')
-  local opts = { buffer = bufnr }
+  local opts = { buf = bufnr }
 
   -- basics: copy/cut/paste/create/rename/remove
   vim.keymap.set('n', 'c', api.fs.copy.node, opts)