Modify get_board_visual function

[HyoungSooo]

Hello zhelyabuzhsky!

I am making a chess game using the stockfish engine in the terminal.
Changed the visual aspect of the chess board as it appears in the terminal.
We added a parameter to the function, which allows you to use both the alphabet version and the 2D character version.
with created test code and it will be passed

2d charactor version

+---+---+---+---+---+---+---+---+
| ♖ | ♘ | ♗ | ♕ | ♔ | ♗ | ♘ | ♖ | 8
+---+---+---+---+---+---+---+---+
| ♙ | ♙ | ♙ |   |   | ♙ | ♙ | ♙ | 7
+---+---+---+---+---+---+---+---+
|   |   |   |   | ♙ |   |   |   | 6
+---+---+---+---+---+---+---+---+
|   |   |   | ♙ |   |   |   |   | 5
+---+---+---+---+---+---+---+---+
|   |   |   | ♟ | ♟ |   |   |   | 4
+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | 3
+---+---+---+---+---+---+---+---+
| ♟ | ♟ | ♟ |   |   | ♟ | ♟ | ♟ | 2
+---+---+---+---+---+---+---+---+
| ♜ | ♞ | ♝ | ♛ | ♚ | ♝ | ♞ | ♜ | 1
+---+---+---+---+---+---+---+---+
  a   b   c   d   e   f   g   h

[HyoungSooo]

test failed on this function test_invalid_fen_king_attacked
test failed fen is "8/8/8/3k4/3K4/8/8/8 b - - 0 1"

but i found stockfish version 9 was return True when call stockfish.is_fen_valid("8/8/8/3k4/3K4/8/8/8 b - - 0 1")
is this correct?

[github-actions]

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stockfish/models.py

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