feat: add support pubspec.lock files for dart (#3344)

Co-authored-by: knqyf263 <knqyf263@gmail.com>

integration/fs_test.go

@@ -147,6 +147,15 @@ func TestFilesystem(t *testing.T) {
 			},
 			golden: "testdata/cocoapods.json.golden",
 		},
+		{
+			name: "pubspec.lock",
+			args: args{
+				securityChecks: "vuln",
+				listAllPkgs:    true,
+				input:          "testdata/fixtures/fs/pubspec",
+			},
+			golden: "testdata/pubspec.lock.json.golden",
+		},
 		{
 			name: "mix.lock",
 			args: args{