Update PR checker to check more for cloud-hosted

[gkwan-ibm]

1. Update PR checker to check that the section line must follow by an empty line.

If do the following,

== What you'll learn
You will learn how to create ...

the cloud-hosted guide will not show the What you'll learn section correctly as

Check the README.adoc like

== What you'll learn

You will learn how to create ...

2. check the following lines without front or tailing spaces:

```bash
```