Feat/submission stepper (#4)

* feat(FormGroup): make underlying FormPanel toggleable prop user configurable

* feat(QuestionStepper): add stepper component enabled by OdkWebForm stepperLayout prop

* feat(QuestionStepper): update stepper layout to be closer to ODK Collect

* bug fix: recompute final step when number of steps change

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Co-authored-by: spwoodcock <sam.woodcock@protonmail.com>

Author: DanielJDufour

packages/web-forms/src/components/QuestionStepper.vue

@@ -60,7 +60,7 @@ const steps = computed(() =>
 
 // Handle stepper state
 const firstStep = 0;
-const finalStep = steps.value.length;
+const finalStep = computed(() => steps.value.length - 1);
 const currentStep = ref(firstStep);
 const submitPressed = ref(false);
 provide('submitPressed', submitPressed);