fix(js_parser): don't panic on declare@

[fireairforce]

Summary

closes: #4562

Now it will panic on:

declare@

so i replace .expect() with .add_diagnostic() at parse_declare.

Test Plan

I add test case for this.

[codspeed-hq]

CodSpeed Performance Report

Merging #4601 will improve performances by 6.09%

_{Comparing fireairforce:fix-4562 (77663bb) with main (486ec39)}

Summary

⚡ 1 improvements
✅ 98 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	fireairforce:fix-4562	Change
⚡	pure_9395922602181450299.css[uncached]	4.3 ms	4.1 ms	+6.09%

[denbezrukov]

🥳🥳🥳