feat(client): add experiment runner context#795

wochinge wants to merge 4 commits intomainlangfuse/langfuse-js:mainfrom

tobias/lfe-9365-implement-js-sdk-changes-runnercontextlangfuse/langfuse-js:tobias/lfe-9365-implement-js-sdk-changes-runnercontextCopy head branch name to clipboard