Fix two examples of using h with components and slots

[skirtles-code]

Description of Problem

Two of the examples in render-function.md have problems, both related to using h with components and slots.

The first example tries to create a component using Vue.h('child'. This won't work because it needs to use resolveComponent.

The second example triggers a warning:

[Vue warn]: Non-function value encountered for default slot. Prefer function slots for better performance.

You can see it yourself here: https://jsfiddle.net/skirtle/ho9t3upv/

When using h to create an HTML element there are various different ways to pass the children. However, when creating a component the children have to be passed as a slot object containing functions, otherwise the warning above is shown.

Proposed Solution

In the first example I have also adjusted the spacing to accommodate the Vue.resolveComponent.

The second example is intended to illustrate how painful it is to write render functions without JSX. As well as fixing the warning, adding the extra complication of the slot object actually helps to reinforce this point.