Check for speakers' slides and update the lectures

[bencodezen]

There should be an easy to access link for each talk on speaker notes if they are available.

Currently in hold for these slides:

• [ ] Opening Keynote - Mina
• [ ] Removing Unwanted CSS - Chris
• [x] Element-First Design - Michael
• [x] Introducing a Design System to a Legacy Product - Paul

[bencodezen]

Currently trying to track down the remaining slides which will be updated in the original post for tracking purposes.

I will close this issue once I've received confirmation on whether the slides will be posted for the talks above.