feat: Add support for toggling readonly mode. (#8750)

* feat: Add methods for toggling and inspecting the readonly state of a workspace.

* refactor: Use the new readonly setters/getters in place of checking the injection options.

* fix: Fix bug that allowed dragging blocks from a flyout onto a readonly workspace.

* feat: Toggle a `blocklyReadOnly` class when readonly status is changed.

* chore: Placate the linter.

* chore: Placate the compiler.

core/dragging/block_drag_strategy.ts

@@ -78,7 +78,7 @@ export class BlockDragStrategy implements IDragStrategy {
     return (
       this.block.isOwnMovable() &&
       !this.block.isDeadOrDying() &&
-      !this.workspace.options.readOnly &&
+      !this.workspace.isReadOnly() &&
       // We never drag blocks in the flyout, only create new blocks that are
       // dragged.
       !this.block.isInFlyout

core/dragging/comment_drag_strategy.ts

@@ -29,7 +29,7 @@ export class CommentDragStrategy implements IDragStrategy {
     return (
       this.comment.isOwnMovable() &&
       !this.comment.isDeadOrDying() &&
-      !this.workspace.options.readOnly
+      !this.workspace.isReadOnly()
     );
   }