Improve relative parent paths handling for sourcemaps

[jeparlefrancais]

Closes #159

• [x] add entry to the changelog

[github-actions[bot]]

Coverage after merging fix-relative-parent-directory into main will be

87.02%

Coverage Report for Changed Files

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src/rules/convert_require
roblox_require_mode.rs	59.69%	100%	70.59%	58.66%	100–103, 105, 108–110, 112, 118–119, 152–159, 162–170, 174, 179–183, 186, 190–195, 198–205, 221–224, 242, 40, 55–62, 72–74, 88–90