fix: solar span too tight

[simon-something]

fix the span used when parsing with solar (which currently is either the item span if the doc comment is missing, or only the doc comment if it does exist)

[codspeed-hq]

CodSpeed Performance Report

Merging #87 will degrade performances by 83.17%

_{Comparing defi-wonderland:fix/solar-span-too-tight (a51e2ca) with fix-solar-differences (523ed62)}

Summary

❌ 4 regressions
✅ 12 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	parse_solar[test-data/BasicSample.sol]	404.5 µs	1,767.5 µs	-77.11%
❌	parse_solar[test-data/InterfaceSample.sol]	182 µs	396.3 µs	-54.08%
❌	parse_solar[test-data/LibrarySample.sol]	154.3 µs	286.1 µs	-46.07%
❌	parse_solar[test-data/ParserTest.sol]	565.8 µs	3,362.7 µs	-83.17%