5. Feature/adding slide in training modules

[omChauhanDev]

What this PR does

This pr help user in adding slides to training modules via dashboard.

The logic for adding slides to training modules is dipicted by this flow diagram :

Screenshots

Before:

After:

1. Add slide button
   

2. Modal for adding slide
   

3. Slide added
   

4. Validations :

• V1 : One slug cannot be taken by two training web pages
  

• V2 : Multiple addition of same slide is not allowed
  

• V3 : No field should be empty
  

[ragesoss]

This works as expected for me. I think it needs to handle the wiki pages a little more flexibly, accept either just the page title or the complete URL, and extracting the page title if a full URL is submitted.