Add a feature idea note to DB.exec(), derived from a forum discussion.

FossilOrigin-Name: 792f43209c4b6e85386b6b3906814b7f2ad310d50ba563b3fd1cb37e55adf8db

ext/wasm/api/sqlite3-api-oo1.js

@@ -183,7 +183,7 @@ self.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
         checkSqlite3Rc(
           pDb, capi.sqlite3_exec(pDb, postInitSql, 0, 0, 0)
         );
-      }      
+      }
     }catch(e){
       this.close();
       throw e;
@@ -791,6 +791,9 @@ self.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
        - `callback` and `resultRows`: permit an array entries with
        semantics similar to those described for `bind` above.
 
+       - If passed neither a callback nor returnValue but is passed a
+         rowMode, default to returning the result set.
+
     */
     exec: function(/*(sql [,obj]) || (obj)*/){
       affirmDbOpen(this);