BrushState (#605)

* BrushState WIP

* Add missing import after merge

* Fix some svelte/type checks

* Update @layerstack/utils with improved clamp() types.  Fix remaining type warnings

* fix merge

* Move BrushState to $lib/states

* Fix CI

* Fix CI

Author: techniq

packages/layerchart/package.json

@@ -85,7 +85,7 @@
     "@layerstack/svelte-actions": "1.0.1-next.14",
     "@layerstack/svelte-state": "0.1.0-next.19",
     "@layerstack/tailwind": "2.0.0-next.17",
-    "@layerstack/utils": "2.0.0-next.14",
+    "@layerstack/utils": "2.0.0-next.15",
     "d3-array": "^3.2.4",
     "d3-color": "^3.1.0",
     "d3-delaunay": "^6.0.4",