Adds a Stepper control and uses it for the steppers in the editor.

app/src/main/res/layout/component_stepper.xml

@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="utf-8"?>
+<merge xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:layout_margin="@dimen/text_margin"
+    tools:context=".ui.components.Stepper">
+
+    <TextView
+        android:id="@+id/text"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:text="20 (+5)" />
+
+    <TextView
+        android:id="@+id/label"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text=""
+        android:textAppearance="?attr/textAppearanceSubtitle1"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:text="Strength" />
+
+    <Button
+        android:id="@+id/decrement"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/label_decrement_field"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toStartOf="@id/increment"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <Button
+        android:id="@+id/increment"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/label_increment_field"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+</merge>