Terrarum User Art format

* Endianness: LITTLE

* Palette colour is encoded as 0b0000RRRR 0bGGGGBBBB (yep, four bits are wasted)

Ord  Hex  Description
00   54   T
01   45   E
02   41   A
03   46   F

04        Colour model
     00   Invalid
     01   16 Colours
     02   64 Colours
     08   User-defined palette

05        Number of swatches
     00 - No palette mode (using defined palette)
        - 256 colours (using user-defined)
     nn - Colour count (0-255; 0 is interpreted as 256)

06        Width of the image (LSB)
07        Width of the image (MSB)

08        Name of the art in UTF-8
...  00   String terminator

...       Name of the author in UTF-8
...  00   String terminator

...       Palette colour 0, if any (0R)
...       Palette colour 0, if any (GB)
...       Palette colour 1, if any (0R)
...       Palette colour 1, if any (GB)
...       Palette colour 2, if any (0R)
...       Palette colour 2, if any (GB)

...       Colour indices, each byte represents each pixel

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