Updating the gradient method to accept Uint8Array

[welll]

Hi, this PR will also support the grad be a Uint8Array

Current Behavior:

cont defaultGradient = {
        0.4: 'blue',
        0.6: 'cyan',
        0.7: 'lime',
        0.8: 'yellow',
        1.0: 'red'
    }

With this PR, the [Object] still supported and it also supports [Uint8Array]

const viridisPallete = new Uint8Array([68,1,84,255,68,2,86,255,69,4,87,255,69,5,89,255,70,7,90,255,70,8,92,255,70,10,93,255,70,11,94,255,71,13,96,255,71,14,97,255,71,16,99,255,71,17,100,255,71,19,101,255,72,20,103,255,72,22,104,255,72,23,105,255,72,24,106,255,72,26,108,255,72,27,109,255,72,28,110,255,72,29,111,255,72,31,112,255,72,32,113,255,72,33,115,255,72,35,116,255,72,36,117,255,72,37,118,255,72,38,119,255,72,40,120,255,72,41,121,255,71,42,122,255,71,44,122,255,71,45,123,255,71,46,124,255,71,47,125,255,70,48,126,255,70,50,126,255,70,51,127,255,70,52,128,255,69,53,129,255,69,55,129,255,69,56,130,255,68,57,131,255,68,58,131,255,68,59,132,255,67,61,132,255,67,62,133,255,66,63,133,255,66,64,134,255,66,65,134,255,65,66,135,255,65,68,135,255,64,69,136,255,64,70,136,255,63,71,136,255,63,72,137,255,62,73,137,255,62,74,137,255,62,76,138,255,61,77,138,255,61,78,138,255,60,79,138,255,60,80,139,255,59,81,139,255,59,82,139,255,58,83,139,255,58,84,140,255,57,85,140,255,57,86,140,255,56,88,140,255,56,89,140,255,55,90,140,255,55,91,141,255,54,92,141,255,54,93,141,255,53,94,141,255,53,95,141,255,52,96,141,255,52,97,141,255,51,98,141,255,51,99,141,255,50,100,142,255,50,101,142,255,49,102,142,255,49,103,142,255,49,104,142,255,48,105,142,255,48,106,142,255,47,107,142,255,47,108,142,255,46,109,142,255,46,110,142,255,46,111,142,255,45,112,142,255,45,113,142,255,44,113,142,255,44,114,142,255,44,115,142,255,43,116,142,255,43,117,142,255,42,118,142,255,42,119,142,255,42,120,142,255,41,121,142,255,41,122,142,255,41,123,142,255,40,124,142,255,40,125,142,255,39,126,142,255,39,127,142,255,39,128,142,255,38,129,142,255,38,130,142,255,38,130,142,255,37,131,142,255,37,132,142,255,37,133,142,255,36,134,142,255,36,135,142,255,35,136,142,255,35,137,142,255,35,138,141,255,34,139,141,255,34,140,141,255,34,141,141,255,33,142,141,255,33,143,141,255,33,144,141,255,33,145,140,255,32,146,140,255,32,146,140,255,32,147,140,255,31,148,140,255,31,149,139,255,31,150,139,255,31,151,139,255,31,152,139,255,31,153,138,255,31,154,138,255,30,155,138,255,30,156,137,255,30,157,137,255,31,158,137,255,31,159,136,255,31,160,136,255,31,161,136,255,31,161,135,255,31,162,135,255,32,163,134,255,32,164,134,255,33,165,133,255,33,166,133,255,34,167,133,255,34,168,132,255,35,169,131,255,36,170,131,255,37,171,130,255,37,172,130,255,38,173,129,255,39,173,129,255,40,174,128,255,41,175,127,255,42,176,127,255,44,177,126,255,45,178,125,255,46,179,124,255,47,180,124,255,49,181,123,255,50,182,122,255,52,182,121,255,53,183,121,255,55,184,120,255,56,185,119,255,58,186,118,255,59,187,117,255,61,188,116,255,63,188,115,255,64,189,114,255,66,190,113,255,68,191,112,255,70,192,111,255,72,193,110,255,74,193,109,255,76,194,108,255,78,195,107,255,80,196,106,255,82,197,105,255,84,197,104,255,86,198,103,255,88,199,101,255,90,200,100,255,92,200,99,255,94,201,98,255,96,202,96,255,99,203,95,255,101,203,94,255,103,204,92,255,105,205,91,255,108,205,90,255,110,206,88,255,112,207,87,255,115,208,86,255,117,208,84,255,119,209,83,255,122,209,81,255,124,210,80,255,127,211,78,255,129,211,77,255,132,212,75,255,134,213,73,255,137,213,72,255,139,214,70,255,142,214,69,255,144,215,67,255,147,215,65,255,149,216,64,255,152,216,62,255,155,217,60,255,157,217,59,255,160,218,57,255,162,218,55,255,165,219,54,255,168,219,52,255,170,220,50,255,173,220,48,255,176,221,47,255,178,221,45,255,181,222,43,255,184,222,41,255,186,222,40,255,189,223,38,255,192,223,37,255,194,223,35,255,197,224,33,255,200,224,32,255,202,225,31,255,205,225,29,255,208,225,28,255,210,226,27,255,213,226,26,255,216,226,25,255,218,227,25,255,221,227,24,255,223,227,24,255,226,228,24,255,229,228,25,255,231,228,25,255,234,229,26,255,236,229,27,255,239,229,28,255,241,229,29,255,244,230,30,255,246,230,32,255,248,230,33,255,251,231,35,255,253,231,37,255])
var heat = simpleheat('canvas').data(data).max(18).gradient(viridisPallete),