refactor file_exists function

[Yagua]

Since this implementation of the file_exists function has the ability to give an answer as to whether or not a file exists, it is not completely accurate since giving the open function a directory path as an argument will still return true indicating that the file exists even though it is not actually a file.

M.file_exists = function(file)
  file = io.open(file, "rb")
  if file then
    file:close()
  end
  return file ~= nil
end

so I refactored the function, making use of the built-in function'vim.fn.filereadable, to ensure that first we are verifying that we are actually reading a file and not a directory, and in turn showing if this file exists or not.

M.file_exists = function(file)
  if vim.fn.filereadable(file) ~= 1 then return false end
  return true
end

In this way when running the read_env_file function and there is a virtual environment (directory) with the name .env in the current directory, only the .env files will be taken into account and not the directory, preventing io.lines from trying to scan a directory.

[NTBBloodbath]

Hey,

This is indeed a great catch, thanks for the refactoring!

I would like the change I suggested to be applied before merging tho, I feel like it's worth it to simplify codebase and improve its readability.

Cheers

[Yagua]

Of course, it looks even better!