update docs

src/test/resources/tests/test_concat.jvcl

@@ -1,5 +1,6 @@
 {
   "assets": [
+    // wildcard matches multiple files, vid1_splits becomes a "list" asset
     { "name": "vid1_splits", "path": "src/test/resources/outputs/vid1_splits_*.mp4" }
   ],
   "operations": [

src/test/resources/tests/test_letterbox.jvcl

@@ -1,5 +1,6 @@
 {
   "assets": [
+    // wildcard matches multiple files, vid1_splits becomes a "list" asset
     { "name": "vid1_splits", "path": "src/test/resources/outputs/vid1_splits_*.mp4" }
   ],
   "operations": [

src/test/resources/tests/test_scale.jvcl

@@ -1,5 +1,6 @@
 {
   "assets": [
+    // wildcard matches multiple files, vid1_splits becomes a "list" asset
     { "name": "vid1_splits", "path": "src/test/resources/outputs/vid1_splits_*.mp4" }
   ],
   "operations": [

src/test/resources/tests/test_trim.jvcl

@@ -1,5 +1,6 @@
 {
   "assets": [
+    // wildcard matches multiple files, vid1_splits becomes a "list" asset
     { "name": "vid1_splits", "path": "src/test/resources/outputs/vid1_splits_*.mp4" }
   ],
   "operations": [