Clarify arguments passed to the template function by the flow.Loop component

Author: FelixHenninger

docs/reference/flow.rst

@@ -92,7 +92,7 @@ Loop
     There are several ways in which this option can be used:
 
     * First it can be a **single component** of any type, an :js:class:`html.Screen`, (most likely) a :js:class:`flow.Sequence` or even another :js:class:`flow.Loop`. This component will be :js:func:`cloned <clone>` for each iteration, and the :js:attr:`parameters <options.parameters>` substituted on each copy so that the repetitions can differ from another.
-    * Second, it can be a **function** that creates and returns the component for each iteration. This function will receive each set of :js:attr:`templateParameters <options.templateParameters>` in turn as a first argument (and, optionally, the index as a second argument). The advantage of this method is a greater flexibility: More logic can be used at every step to customize every iteration.
+    * Second, it can be a **function** that creates and returns the component for each iteration. This function will receive each set of :js:attr:`templateParameters <options.templateParameters>` in turn as a first argument (and, optionally, the index as a second argument, and the loop component itself as a third). The advantage of this method is a greater flexibility: Additional logic can be used at every step to customize every iteration.
 
   .. js:attribute:: options.templateParameters
 

library/src/flow.js

@@ -148,7 +148,7 @@ export class Loop extends Sequence {
       })
     } else if (isFunction(this.options.template)) {
       this.options.content = this.options.templateParameters.map(
-        p => this.options.template(p, this),
+        (p, i) => this.options.template(p, i, this),
       )
     } else {
       console.warn('Missing or invalid template in loop, no content generated')