It started slowly with some jokes about side parts. Next, came the word “cheugy” and making fun of “business casual clubwear.” But coming after mom jeans? For millennials, that meant war. Back in October, creator @indigotshai (who happens to be a millennial herself — the betrayal!) released a video about styles that age millennials. In it, she shows a street style image of a woman wearing a black sweater, tucked into her high-waisted jeans, and …