Improve the GH Action error display

[jyasskin]

https://github.com/WICG/shared-storage/actions/runs/3137508744/jobs/5095759053 shows an error of:

whose text is:

...
▶Run echo "::group::Generate Static HTML"
▶Generate Static HTML
▶Run actions/upload-artifact@v2
With the provided path, there will be 1 file uploaded
Starting artifact upload
For more detailed logs during the artifact upload process, enable step-debugging: https://docs.github.com/actions/monitoring-and-troubleshooting-workflows/enabling-debug-logging#enabling-step-debug-logging
Artifact name is valid!
Container for artifact "spec-prod-result" successfully created. Starting upload of file(s)
Total size of all the files uploaded is 10460 bytes
File upload process has finished. Finalizing the artifact upload
Artifact has been finalized. All files have been successfully uploaded!

The raw size of all the files that were specified for upload is 57956 bytes
The size of all the files that were uploaded is 10460 bytes. This takes into account any gzip compression used to reduce the upload size, time and storage

Note: The size of downloaded zips can differ significantly from the reported size. For more information see: https://github.com/actions/upload-artifact#zipped-artifact-downloads 

Artifact spec-prod-result has been successfully uploaded!
▶Run echo "::group::Validate markup"
▶Validate markup
▶Run echo "::group::Validate pubrules (Specberus)"
▶Validate pubrules (Specberus)
▶Run echo "::group::Validate Web IDL"
▶Validate Web IDL
▶Run # Failed
Error: Failed. See details above.
Error: Process completed with exit code 1.

Users have to know to expand the "Validate Web IDL" entry in order to see the error message.

I don't know if this is even possible with GH Actions, but it'd be nice if spec-prod could ensure that the actual error is visible in the first load of a failed Action run.

[sidvishnoi]

It's not possible to improve the display of logs as of now (#1), but I've #133 planned for weekend.

[sidvishnoi]

Closing in favour of #133.