add slnx support #579

Job	Run time
check_code_format	49s
check_licenses_net472 (App)	2m 3s
check_version_command (net6.0)	20s
check_licenses (net6.0, App)	32s
check_licenses_net472 (Tests)	3m 38s
check_version_command_net472	2m 16s
check_version_command (net8.0)	26s
check_licenses_net472 (ProjectWithReferenceContainingLicenseExpression)	1m 54s
check_licenses (net6.0, Tests)	31s
check_version_command (net9.0)	28s
check_licenses (net6.0, ProjectWithReferenceContainingLicenseExpression)	29s
test (ubuntu-latest, net6.0)	22s
check_licenses (net8.0, App)	32s
test_windows (net6.0)	1m 55s
test (ubuntu-latest, net8.0)	16s
check_licenses (net8.0, Tests)	34s
test_windows (net8.0)	1m 49s
test (ubuntu-latest, net9.0)	16s
check_licenses (net8.0, ProjectWithReferenceContainingLicenseExpression)	23s
test_windows (net472)	1m 55s
test (macos-latest, net6.0)	47s
check_licenses (net9.0, App)	35s
test_windows (net9.0)	1m 54s
test (macos-latest, net8.0)	53s
check_licenses (net9.0, Tests)	30s
test (macos-latest, net9.0)	46s
check_licenses (net9.0, ProjectWithReferenceContainingLicenseExpression)	22s
	27m 15s

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