[FLINK-2751] [Documentation] Add quickstart menu to the navigation bar

[rerngvit]

Add quickstart menu to the navigation bar for Flink documentation

[chiwanpark]

Hi @rerngvit, Thanks for sending pull request. But your pull request has some problems.

First, {{ quickstart }} is not defined in your changes. As you can see in 19-22 lines of navbar.html, you should define {{ quickstart }}.

Second, there is no conditional active class for quickstart dropdown menu. Please include conditional active class in quickstart dropdown menu. Conditional active classes for other menus are in line 55 of navbar.html.

[rerngvit]

@chiwanpark Thanks for reviewing this issue. I modified the pull request according to your comments. Please have a look.

[chiwanpark]

Hi @rerngvit, I have tested your pull request.

Because setup_quickstart.html contains "setup" keyword in url, there are two active menus (Quickstart, Setup) when we open Quickstart: Setup page. I found a solution like following:

<li class="dropdown{% if page.url contains '/quickstart/' %} active{% endif %}">

The solution must be applied not only quickstart but also other dropdown menus such as setup, programming guide, ..., etc..

BTW, there is a typo line 68 of navbar.html. The a tag must be closed. I know this is not related to your changes but fixing it would be better.

After addressing this, we can merge this pull request. :-)

[rerngvit]

@chiwanpark Thanks for reviewing this issue. I revised the pull request according to your comments. Please have a look.

[chiwanpark]

Looks good to merge. I'll merge this.

[mxm]

Looks good. Thanks for the contribution @rerngvit!