feat: allow custom headers in urlopener + pass to it from urlopen#770

seemab-yamin wants to merge 3 commits intoAnswerDotAI:mainAnswerDotAI/fastcore:mainfrom

seemab-yamin:fix-net-urlopener-add-missing-header-paramseemab-yamin/fastcore:fix-net-urlopener-add-missing-header-paramCopy head branch name to clipboard