scripts/entity-example.md: Fix MD041 warnings

The following warnings are generated by using markdownlint analysis:
```
scripts/entity-example.md:1 MD041/first-line-heading/first-line-h1 First line in a file should be a top-level heading [Context: "If your platform requires the ..."]
```
Refer to markdown-lint [1] to fix MD041
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/041-first-line-h1.md

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: Ie58bdbff68235b348fe82432614fd351ba1c6141