Create shortcode for posting the question on frontend

[geek92sunny]

1. We have already created shortcode to list QAs.
2. Now we will create the shortcode to generate the form to post the question.
3. It will produce this form and function exactly like this.

4. Similar to QA list shortcode, this shortcode will accept an optional parameter for product ID.

Don't duplicate the code, the core code that renders and handles the form must be the same.