fix(completion): dotnu_completion for nested folders/scripts #15

Job	Run time
fmt-clippy (windows-latest)	6m 40s
tests (windows-latest)	11m 19s
fmt-clippy (macos-13)	4m 33s
tests (macos-latest)	4m 42s
fmt-clippy (ubuntu-20.04)	3m 4s
tests (ubuntu-20.04)	6m 27s
plugins (windows-latest)	14m 52s
std-lib-and-python-virtualenv (ubuntu-20.04, py)	4m 12s
plugins (macos-13)	9m 8s
Build WASM	2m 7s
std-lib-and-python-virtualenv (macos-latest, py)	5m 18s
plugins (ubuntu-20.04)	6m 9s
Clippy WASM	2m 14s
std-lib-and-python-virtualenv (windows-latest, py)	13m 26s
	1h 34m 11s

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