feat: add on_not_selected callback

[woodgear]

[kiyoon]

Thank you. What do you think is the use case for this one?

[woodgear]

to distinguish between an internal error of Neovim/Treesitter and a mismatch between the current buffer and the query string . for example

  require("xxx").setup {
    | (where the cursor)
  }

i thought the setup is "function.inner",but in fact is not. it take me sometimes to figure out, the treesitter-textobject works prepectly. it just has not to match the query string