feat: add shorthand notation example to playground

[sberan]

Add a new "shorthand" example tab that demonstrates using type
strings directly (e.g., schema('string')) instead of full object
notation. Also update extractSchemaFromCode to parse shorthand syntax.

[github-actions]

Benchmark Results

Only tests where both validators pass are compared (apples-to-apples)

tjs vs ajv

Draft	Tests	tjs	ajv	Winner
draft4	790	27.8M	13.2M	🟢 tjs 2.11×
draft6	1120	30.1M	14.9M	🟢 tjs 2.02×
draft7	1324	28.0M	13.5M	🟢 tjs 2.07×
draft2019-09	1703	25.0M	6.4M	🟢 tjs 3.93×
draft2020-12	1665	27.6M	6.8M	🟢 tjs 4.08×

Overall: 🟢 tjs is 3.09× faster on 6602 shared tests

tjs vs is-my-json-valid

Draft	Tests	tjs	is-my-json-valid	Winner
draft4	640	37.5M	14.8M	🟢 tjs 2.53×
draft6	703	38.1M	16.6M	🟢 tjs 2.29×
draft7	732	45.9M	19.0M	🟢 tjs 2.42×
draft2019-09	842	44.9M	20.6M	🟢 tjs 2.18×
draft2020-12	785	46.8M	20.2M	🟢 tjs 2.32×

Overall: 🟢 tjs is 2.34× faster on 3702 shared tests

tjs vs djv

Draft	Tests	tjs	djv	Winner
draft4	540	38.4M	3.7M	🟢 tjs 10.43×
draft6	706	40.4M	3.6M	🟢 tjs 11.12×
draft7	760	43.6M	4.0M	🟢 tjs 10.85×
draft2019-09	868	42.0M	4.9M	🟢 tjs 8.58×
draft2020-12	843	45.5M	4.6M	🟢 tjs 9.83×

Overall: 🟢 tjs is 10.09× faster on 3717 shared tests

tjs vs jsen

Draft	Tests	tjs	jsen	Winner
draft4	671	36.0M	15.0M	🟢 tjs 2.40×
draft6	707	36.6M	15.6M	🟢 tjs 2.35×
draft7	736	43.8M	17.8M	🟢 tjs 2.46×
draft2019-09	838	42.6M	17.0M	🟢 tjs 2.52×
draft2020-12	792	45.6M	18.0M	🟢 tjs 2.54×

Overall: 🟢 tjs is 2.45× faster on 3744 shared tests

tjs vs schemasafe

Draft	Tests	tjs	schemasafe	Winner
draft4	821	27.9M	21.6M	🟢 tjs 1.29×
draft6	1104	29.8M	23.4M	🟢 tjs 1.27×
draft7	1238	31.3M	21.1M	🟢 tjs 1.48×
draft2019-09	1641	27.8M	18.9M	🟢 tjs 1.47×
draft2020-12	1540	27.6M	15.2M	🟢 tjs 1.81×

Overall: 🟢 tjs is 1.50× faster on 6344 shared tests