chore: deprecation notice for builtin.file_browser (#1574)

`builtin.file_browser` will be removed in favor of `telescope-file-browser.nvim`.
Primary rationale for carving out the file browser to an extension:
- Faster development
- Very expansive picker with larger feature set than builtins

lua/telescope/builtin/files.lua

@@ -284,6 +284,9 @@ local function prepare_match(entry, kind)
 end
 
 files.file_browser = function(opts)
+  vim.api.nvim_err_writeln [[Deprecation notice: file browser will be carved out into a more featureful extension, see:
+https://github.com/nvim-telescope/telescope-file-browser.nvim]]
+
   opts = opts or {}
 
   local is_dir = function(value)

lua/telescope/builtin/init.lua

@@ -94,6 +94,7 @@ builtin.fd = builtin.find_files
 ---     - Note: you can create files nested into several directories with `<C-e>`, i.e. `lua/telescope/init.lua` would
 ---       create the file `init.lua` inside of `lua/telescope` and will create the necessary folders (similar to how
 ---       `mkdir -p` would work) if they do not already exist
+---@deprecated Please move to https://github.com/nvim-telescope/telescope-file-browser.nvim
 ---@param opts table: options to pass to the picker
 ---@field cwd string: root dir to browse from (default: cwd, use utils.buffer_dir() to search relative to open buffer)
 ---@field depth number: file tree depth to display (default: 1)