refactor: add constructor to fix jest test failing

See: facebook/react-native#22175 (comment)

src/model/TextBlock.ts

@@ -1,9 +1,10 @@
 import Block from './Block'
-import { TextAttributesMap, BlockAttributesMap } from '@delta/attributes'
+import Document from './Document'
+import { TextAttributesMap } from '@delta/attributes'
 import { boundMethod } from 'autobind-decorator'
 import { Selection } from '@delta/selection'
 import TextTransformsRegistry from '@core/TextTransformsRegistry'
-import { DeltaChangeContext } from '@delta/DocumentDelta';
+import { DeltaChangeContext } from '@delta/DocumentDelta'
 
 export default class TextBlock<T extends string> extends Block<T> {
 
@@ -14,6 +15,12 @@ export default class TextBlock<T extends string> extends Block<T> {
   }
   private length: number = 0
 
+  constructor(
+    blockInterface: Document.BlockInterface<T>
+  ) {
+    super(blockInterface)
+  }
+
   getSelection(): Selection {
     // TODO inspect dependencies and refactor
     return this.selection
@@ -43,7 +50,6 @@ export default class TextBlock<T extends string> extends Block<T> {
 
   @boundMethod
   handleOnTextChange(newText: string, context: DeltaChangeContext): void {
-    // Sanitize newText here
     const updatedDelta = this.getDelta().applyTextDiff(newText, context)
     this.updateDelta(updatedDelta)
     this.length = newText.length