Add Lively Properties JSON Schema

[dejohansson]

• Not sure where the schema should be placed so I put it in the root folder for now.
• I haven't been able to figure out what the "tick" property on the slider setting does so I left its description empty for now.

[CLAassistant]

All committers have signed the CLA.

[dejohansson]

This adds the JSON schema discussed in #1468

[rocksdanister]

maybe its better to create a schemas folder in root and move it ther?
"tick" was used to show intervals in slider UI, no longer being used now.

[dejohansson]

maybe its better to create a schemas folder in root and move it ther?

Sounds good 👍 It's moved now.

"tick" was used to show lines in the UI for step, no longer being used now.

Alright, I removed the property from the schema. I assume it should also be removed from the wiki (here and here) to mitigate confusion in the future?

[rocksdanister]

Looks good 🥳