Add local build/dev tests for examples

[CahidArda]

Added CI tests which do the following:

• run the untittests
• build the workflow-js project
• install the local build in all examples and run npm run build and npm run dev
• make a ci release
• run workflows with the ci release in examples/ci, examples/cloudflare-workers-hono, examples/nextjs-12 and examples/nextjs-pages.

There are also a number of fixes:

• serve for nextjs pages router doesn't stringify all bodies anymore. it returns strings as they are, undefined as it is and stringifies the rest
• triggerFirstInvocation uses publish instead of publishJSON so that a content type header can be set (publishJSON sets the content type to application/json)
• fixes failure callback retry and forwards user headers to failure callback

[CahidArda]

reproduced the crypto is not defined error in the last tests

[CahidArda]

as we discussed the changes in this PR with dx and workflow team, I am merging the PR.