add slnx support #584

Job	Run time
check_licenses_net472 (App)	2m 46s
check_version_command (net6.0)	25s
check_code_format	48s
check_licenses_net472 (Tests)	2m 58s
check_licenses (net6.0, App)	28s
check_version_command (net8.0)	24s
check_licenses_net472 (ProjectWithReferenceContainingLicenseExpression)	1m 56s
check_version_command (net9.0)	25s
check_licenses (net6.0, Tests)	25s
check_version_command_net472	3m 28s
check_licenses (net6.0, ProjectWithReferenceContainingLicenseExpression)	25s
check_licenses (net8.0, App)	37s
test_windows (net6.0)	7m 55s
test (ubuntu-latest, net6.0)	1m 34s
check_licenses (net8.0, Tests)	33s
test_windows (net8.0)	8m 1s
test (ubuntu-latest, net8.0)	1m 51s
check_licenses (net8.0, ProjectWithReferenceContainingLicenseExpression)	31s
test_windows (net472)	8m 4s
test (ubuntu-latest, net9.0)	1m 32s
check_licenses (net9.0, App)	38s
test_windows (net9.0)	6m 40s
test (macos-latest, net6.0)	1m 44s
check_licenses (net9.0, Tests)	25s
test (macos-latest, net8.0)	1m 42s
test (macos-latest, net9.0)	1m 50s
check_licenses (net9.0, ProjectWithReferenceContainingLicenseExpression)	22s
	58m 27s

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