Fix :escape_formula examples that ignore tabs and CRs

[kidq330]

Docs and tests use escape_sequence: ~w(@ + - = \r \t) which actually omits \r and \t:

escapes = ~w(@ + - = \t \r)

NimbleCSV.define(
  Parser1,
  NimbleCSV.RFC4180.options()
  |> Keyword.merge(escape_formula: %{escapes => "'"})
)

[["\t=1+1"]] |> Parser1.dump_to_iodata() |> IO.iodata_to_binary()

NimbleCSV.define(
  Parser2,
  NimbleCSV.RFC4180.options()
  |> Keyword.merge(escape_formula: %{["@", "+", "-", "=", "\r", "\t"] => "'"})
)

[["\t=1+1"]] |> Parser2.dump_to_iodata() |> IO.iodata_to_binary()

iex(1)> escapes = ~w(@ + - = \t \r)
["@", "+", "-", "="]
iex(2)> NimbleCSV.define(
...(2)>   Parser1,
...(2)>   NimbleCSV.RFC4180.options()
...(2)>   |> Keyword.merge(escape_formula: %{escapes => "'"})
...(2)> )
{:module, Parser1,
 <<70, 79, 82, 49, 0, 0, 67, 252, 66, 69, 65, 77, 65, 116, 85, 56, 0, 0, 3, 209,
   0, 0, 0, 84, 14, 69, 108, 105, 120, 105, 114, 46, 80, 97, 114, 115, 101, 114,
   49, 8, 95, 95, 105, 110, 102, 111, 95, ...>>, :ok}
iex(3)> [["\t=1+1"]] |> Parser1.dump_to_iodata() |> IO.iodata_to_binary()
"\t=1+1\r\n"
iex(4)> NimbleCSV.define(
...(4)>   Parser2,
...(4)>   NimbleCSV.RFC4180.options()
...(4)>   |> Keyword.merge(escape_formula: %{["@", "+", "-", "=", "\r", "\t"] => "'"})
...(4)> )
{:module, Parser2,
 <<70, 79, 82, 49, 0, 0, 68, 60, 66, 69, 65, 77, 65, 116, 85, 56, 0, 0, 3, 209,
   0, 0, 0, 84, 14, 69, 108, 105, 120, 105, 114, 46, 80, 97, 114, 115, 101, 114,
   50, 8, 95, 95, 105, 110, 102, 111, 95, ...>>, :ok}
iex(5)> [["\t=1+1"]] |> Parser2.dump_to_iodata() |> IO.iodata_to_binary()
"'\t=1+1\r\n"

[josevalim]

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