Ignoring code chunk backticks and sending multi-paragraph sections

[arnold-c]

This is just a small extension to #380 to adapt it to work with different code chucks, as well as work when there aren't empty lines either side of the code chunk.

function paragraph_select()
  vim.cmd.norm '{'
  local toplinenr = vim.api.nvim_win_get_cursor(0)[1]
  vim.cmd.norm '}'
  local botlinenr = vim.api.nvim_win_get_cursor(0)[1] - 1
  local lines = vim.api.nvim_buf_get_lines(0, toplinenr, botlinenr, false)

  local start = toplinenr + 1
  local finish = botlinenr
  for k, v in ipairs(lines) do
    if string.find(v, '```{.*}') then
      start = start + k
    end
    if string.match(v, '^```$') then
      finish = toplinenr + k - 1
    end
  end

  vim.cmd(':' .. start)
  vim.cmd.norm 'V'
  vim.cmd(':' .. finish)
end

I had tried to play around with different selections that would allow for multi-paragraph selection e.g., in the middle of a function where there might be breaks for clarity (like the function above), but I couldn't figure out a way to get Treesitter to work consistently in R: vai selects functions, with their label, well, but doesn't work well with pipes as it always selects the next node in addition to the pipe. For the time being I'll just call vai to manually select and send functions. If anyone has some other suggestions they're more than welcome!