Update "Line Grid"

* Rename "Line Grid" to "Line Grid Level 1"
* Change id from css-line-grid to css-line-grid-1
* Move "CSS Level 3?" to "New CSS Level 1"
Update "Scoping Level 1"

* Change id from css-scoping to css-scoping-1
Update "Scroll Snap Points Level 1"

* Change id from css-snappoints to css-snappoints-1
Update "Custom Properties for Cascading Variables Level 1"