🚶 Events - migrate SharePoint list data to Tina

[wicksipedia]

Currently the Events are sourced from a SharePoint list - this isn't ideal since:

• we need to query an external source
• it makes it harder to create a new event first add an image to the website, then add data to a list if you do it too quickly, it can cause tests to fail on deployment due to broken images
• this will help perf stats as next will be able to optimise them

### Tasks
- [x] Create `event` collection
- [x] Write script to export SharePoint event list and presenter data
- [x] Standardise event thumbnail location (in schema)
- [x] Reference TinaCMS event data for events and Live UG
- [x] Remove unused environment variables from build
- [ ] Update marketing standard (give Camilla a video)

[Calinator444]

@wicksipedia

There's a bug in the staging slot. The initial list of events isn't being pulled using Static Site Generation, causing performance to take a nose dive. This needs to be fixed before we finish this.

[Calinator444]

I have created a video describing the new editing workflow. Currently waiting for approval from Seth.

https://www.youtube.com/watch?v=F42rMIpvAZM

[Calinator444]

@wicksipedia I got a text pass from @sethdaily on the how to video for adding events in Tina.

However I haven't updated the readme to explaining how to do this yet.

Seth has already updated the standard for adding events.

How to video for adding events in Tina:

https://www.youtube.com/watch?v=F42rMIpvAZM