make function M.files(winnr, with_content) accept the option table to finetune folders for context

[exrezzo]

while playing with contexts configuration, I found I needed more control over what files and folders should be set as context.
More specifically, I work with projects having hidden folders that actually contain important code, (e.g. /.deployment folder that contains files about deployment).

To overcome this, I momentarily created a "clone" function starting from the existing, public one, that is used as resolve for the file context:

function M.filesHidden(winnr, with_content)
  local cwd = utils.win_cwd(winnr)

  notify.publish(notify.STATUS, 'Scanning files')

  local files = utils.scan_dir(cwd, {
    hidden = true,
    add_dirs = false,
    respect_gitignore = true,
  })

  notify.publish(notify.STATUS, 'Reading files')

  local out = {}

  -- Create file list in chunks
  local chunk_size = 100
  for i = 1, #files, chunk_size do
    local chunk = {}
    for j = i, math.min(i + chunk_size - 1, #files) do
      table.insert(chunk, files[j])
    end

    local chunk_number = math.floor(i / chunk_size)
    local chunk_name = chunk_number == 0 and 'file_map' or 'file_map' .. tostring(chunk_number)

    table.insert(out, {
      content = table.concat(chunk, '\n'),
      filename = chunk_name,
      filetype = 'text',
    })
  end

  -- Read all files if we want content as well
  if with_content then
    async.util.scheduler()

    files = vim.tbl_filter(
      function(file)
        return file.ft ~= nil
      end,
      vim.tbl_map(function(file)
        return {
          name = utils.filepath(file),
          ft = utils.filetype(file),
        }
      end, files)
    )

    for _, file in ipairs(files) do
      local file_data = get_file(file.name, file.ft)
      if file_data then
        table.insert(out, file_data)
      end
    end
  end

  return out
end

that's because I could set up the block where we state the directories to be scanned, making it like so:

local files = utils.scan_dir(cwd, {
    hidden = true,
    add_dirs = false,
    respect_gitignore = true,
  })

I wanted here to still respect .gitignore, but include also hidden files.
WDYT about having the configuration table that's used within utils.scan_dir as a parameter of the function function M.files(winnr, opts, with_content)?

[deathbeam]

#845 Should be solved in