Multi Point Lines (based on Multi Point Arrows) (#660)

* Enable multi points in lines

* Stop retrieving arrow points for lines

* Migrate lines to new spec during load

* Clean up and refactor some code

- Normalize shape dimensions during load
- Rename getArrowAbsoluteBounds

* Fix linter issues

src/scene/data.ts

@@ -7,7 +7,7 @@ import { ExportType, PreviousScene } from "./types";
 import { exportToCanvas, exportToSvg } from "./export";
 import nanoid from "nanoid";
 import { fileOpen, fileSave } from "browser-nativefs";
-import { getCommonBounds } from "../element";
+import { getCommonBounds, normalizeDimensions } from "../element";
 
 import { Point } from "roughjs/bin/geometry";
 import { t } from "../i18n";
@@ -291,6 +291,19 @@ function restore(
           [element.width, element.height],
         ];
       }
+    } else if (element.type === "line") {
+      // old spec, pre-arrows
+      // old spec, post-arrows
+      if (!Array.isArray(element.points) || element.points.length === 0) {
+        points = [
+          [0, 0],
+          [element.width, element.height],
+        ];
+      } else {
+        points = element.points;
+      }
+    } else {
+      normalizeDimensions(element);
     }
 
     return {