Preheat oven to 350 degrees F (175 degrees C). Grease mini-muffin pan with cooking spray. Sift together the flour, brown sugar, white sugar, cinnamon, ginger, nutmeg, baking soda, baking powder, and salt into a large bowl. Whisk together the eggs, butter, and pumpkin in a separate bowl. Mix the flour mixture with the egg mixture. Stir in the butterscotch chips; pour into each cup of the muffin pan to about 3/4 full. Bake in preheated oven until a toothpick inserted into the center of a muffin comes out clean, 10 to 12 minutes.