feat: license file search (#4327)

Signed-off-by: Keith Zantow <kzantow@gmail.com>

syft/pkg/cataloger/internal/licenses/names_test.go

@@ -0,0 +1,45 @@
+package licenses
+
+import (
+	"testing"
+)
+
+func Test_IsLicenseFile(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  bool
+	}{
+		// positive cases (should be detected as license files)
+		{"plain LICENSE", "LICENSE", true},
+		{"lowercase license", "license", true},
+		{"license with extension", "LICENSE.txt", true},
+		{"mixed case", "LiCeNsE", true},
+		{"copying", "COPYING", true},
+		{"AL2.0", "AL2.0", true},
+		{"notice", "NOTICE", true},
+		{"mit-license", "MIT-License", true},
+		{"unlicense", "UNLICENSE", true},
+		{"licence variant", "LICENCE", true},
+		{"license markdown", "license.md", true},
+
+		// negative cases (should NOT be detected)
+		{"AL1.0", "AL1.0", false},
+		{"readme", "README", false},
+		{"readme with ext", "README.md", false},
+		{"not a license", "not_a_license", false},
+		{"licensor (prefix-like but not)", "LICENSOR", false},
+		{"too short (below minLength)", "a", false},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			got := IsLicenseFile(tt.input)
+			if got != tt.want {
+				t.Fatalf("IsLicenseFile(%q) = %v, want %v", tt.input, got, tt.want)
+			}
+		})
+	}
+}