chore(docs): update Steps doc

- Strange errors of examples `ExSimple` and `ExDynamic` of `Steps`
  are fixed.
- In `docs/pages/components/steps/examples/ExSimple.vue`,
    - I got a maximum recursion exceeded error when the `type` prop
      of the second step "Profile" was directly bound to
      `{'is-success': isProfileSuccess}`. The error is not caused
      if the `type` prop value is given via a computed value
      `profileType`. I am not sure if this could be a bug of Vue 3.
- In `docs/pages/components/steps/examples/ExDynamic.vue`,
    - I got a maximum recursive exceeded error if the `visible` prop
      became `undefined`. The error is not caused if the `visible`
      prop is `true` or `false`. I am not sure if this could be a
      bug of Vue 3.
    - The new prop `order` is specified to maintain the ordering of
      items.

docs/pages/components/steps/examples/ExDynamic.vue

@@ -10,12 +10,13 @@
             <b-switch v-model="showGames"> Show games item (by using the visible property) </b-switch>
         </div>
         <b-steps v-model="activeStep">
-            <template v-for="(step, index) in steps">
+            <template v-for="(step, index) in steps" :key="index">
                 <b-step-item
                     v-if="step.displayed"
-                    :key="index"
-                    :visible="step.visible"
-                    :label="step.label">
+                    :visible="step.visible !== undefined ? step.visible : true"
+                    :label="step.label"
+                    :order="index"
+                >
                     {{ step.content }}
                 </b-step-item>
             </template>

docs/pages/components/steps/examples/ExSimple.vue

@@ -69,7 +69,7 @@
                 Lorem ipsum dolor sit amet.
             </b-step-item>
 
-            <b-step-item step="2" label="Profile" :clickable="isStepsClickable" :type="{'is-success': isProfileSuccess}">
+            <b-step-item step="2" label="Profile" :clickable="isStepsClickable" :type="profileType">
                 <h1 class="title has-text-centered">Profile</h1>
                 Lorem ipsum dolor sit amet.
             </b-step-item>
@@ -130,6 +130,14 @@
                 labelPosition: 'bottom',
                 mobileMode: 'minimalist'
             }
+        },
+        computed: {
+            profileType() {
+                // I got a maximum recursion exceeded error, if the following
+                // object is directly specified to the `type` prop of the
+                // "Profile" b-step-item.
+                return { 'is-success': this.isProfileSuccess }
+            }
         }
     }
 </script>