ENH: Define a channel column for events

Author: effigies

src/schema/objects/columns.yaml

@@ -45,6 +45,14 @@ cardiac:
   description: |
     continuous pulse measurement
   type: number
+channel:
+  name: channel
+  display_name: Channel
+  description: |
+    Channel(s) associated with an event.
+    If multiple channels are specified, separate with commas (`,`) or a
+    delimiter specified in the `"Delimiter"` field describing the `channel`
+    column.
 color:
   name: color
   display_name: Color label

src/schema/rules/tabular_data/task.yaml

@@ -10,6 +10,11 @@ TaskEvents:
     response_time: optional
     HED: optional
     stim_file: optional
+    channel:
+      level: optional
+      description_addendum: |
+        Note that this column only applies to data types where
+        channels are specified, such as EEG, iEEG, MEG or NIRS.
   additional_columns: allowed
   initial_columns:
     - onset