docs: clarify fork-to-main repository contribution workflow for external contributors#2

Copilot wants to merge 2 commits intocopilot/fix-1e0bfe56-e0d7-494e-9231-297f2d98cf55alexmadPDE/aws-toolkit-jetbrains:copilot/fix-1e0bfe56-e0d7-494e-9231-297f2d98cf55from

copilot/fix-5e12f270-b763-427d-97be-55c4f2a1de6calexmadPDE/aws-toolkit-jetbrains:copilot/fix-5e12f270-b763-427d-97be-55c4f2a1de6cCopy head branch name to clipboard