fea/add spec validation for the examples

[mimir-d]

• fix extension example since it was outputting a string extension which is invalid, per the spec (also a test)
• fix the typing to disallow primitive types for extension content
• added scripts/check.sh for easier validation before github actions get to run on any PRs
• fixes add validation against the schema from ocp-diag-core #5, Sample output violates the spec #12

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
src/ocptv
__init__.py	2	0	100%
api.py	8	0	100%
formatter.py	12	0	100%
src/ocptv/output
__init__.py	8	0	100%
config.py	54	0	100%
dut.py	63	0	100%
emit.py	65	0	100%
measurement.py	48	0	100%
objects.py	254	0	100%
run.py	73	0	100%
runtime_checks.py	94	0	100%
source.py	28	0	100%
step.py	74	0	100%
TOTAL	783	0	100%