Generate Spans for jobs in multi-job flows

[fitz-vivodyne]

Is your feature request related to a problem? Please describe.

I'm testing out the project on a multi-job workflow.
Following the documentation in the README appears to only create the init events.

This leaves you with a trace that only has a few sparse init events along a very empty timeline.

Describe the solution you'd like

Generate spans for each job within a multi-workflow build

Describe alternatives you've considered

Alternatively you could add manual instrumentation to each job in the workflow, but that adds more repetitive noise.

Additional context
It looks like the postRun code is only called if the trace is supposed to end:

gha-buildevents/src/index.ts

Lines 102 to 106 in e891e91

	if (!isPost) {
	run()
	} else if (isPost && endTrace) {
	runPost()
	}

I'm thinking there should always be a post run function to close a span, but conditionally close the trace.