Symbol loading speed improvement

Symbols valid indexes can be easily cached instead of being checked at each step as such:

  var SYMBOL_CACHE = Array.from(SYMBOL_TILES).map((symbol) => {
      const scale = MINIFY_SCALE_SYMBOL;
      const tileW = TILE_SIZE * scale;
      const centerX = scale - SYMBOL_W >> 1;
      const centerY = scale - SYMBOL_H >> 1;
      const cache = []
      for (let sy = 0; sy < SYMBOL_H; sy++) {
          for (let sx = 0; sx < SYMBOL_W; sx++) {
              const bit_idx = sy * SYMBOL_W + sx;
              const bit = symbol >>> bit_idx & 1;

              if (!bit) continue;

              const precomputeX = (sx + centerX) * 4;
              const precomputeY = (sy + centerY) * 4 * tileW;

              cache.push(precomputeX + precomputeY);
          }
      }
      return cache;
  });

And then in buildOverlayDataForChunkUnified instead of the double for loop we can have

SYMBOL_CACHE[colorIndex].forEach((precomputed_idx) => {
    const outIdx = precomputed_idx + 4 * tileX + 4 * tileY * tileW;
    outData[outIdx] = a_r;
    outData[outIdx + 1] = a_g;
    outData[outIdx + 2] = a_b;
    outData[outIdx + 3] = 255;
});

Indeed this implementation ignores if (outX >= 0 && outX < tileW && outY >= 0 && outY < tileH) check but from my limited testing that is never hit

And probably should not be hit as long as the symbols are defined correctly, but most likely the check can also be added with this caching method