Update partner README, add TypeScript typings, and migrate webhook flows to v3 upsert#89

vivek-gofynd wants to merge 3 commits intomaingofynd/fdk-extension-javascript:mainfrom

codex/review-and-suggest-improvements-for-extension-librarygofynd/fdk-extension-javascript:codex/review-and-suggest-improvements-for-extension-libraryCopy head branch name to clipboard