Doc: supplement the document content.

[textGamex]

Pull request type

Please check the type of change your PR introduces:

• [ ] Update
• [ ] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [x] Documentation content changes

What is the current behavior?

Issue Number: N/A

What is the new behavior?

add NavigationView Doc:

• Set initial page
• NavigationView with MVVM Pattern Explanation

Other information

[textGamex]

Should the example code in the documentation be concise or complete?

[pomianowski]

Should the example code in the documentation be concise or complete?

I think it should be simple with links to sample programs. In RC 4 the samples directory will contain more code examples

[textGamex]

Should the example code in the documentation be concise or complete?

I think it should be simple with links to sample programs. In RC 4 the samples directory will contain more code examples

So is this pull request inappropriate?