Clarify handling of filtered terminals

docs/tree_construction.md

@@ -22,6 +22,23 @@ Lark filters out certain types of terminals by default, considering them punctua
 
     - Unnamed regular expressions (like `/[0-9]/`)
     - Named terminals whose name starts with a letter (like `DIGIT`)
+    - All terminals concatenated within a terminal
+
+**Example:**
+```
+start:  PNAME pname
+
+PNAME:  "(" NAME ")"
+pname:  "(" NAME ")"
+
+NAME:   /\w+/
+%ignore /\s+/
+```
+Lark will parse "(Hello) (World)" as:
+
+    start
+        (Hello)
+        pname World
 
 Rules prefixed with `!` will retain all their literals regardless.