implement search-marker prototype (limited usage for now)

src/structs/ContentFormat.js

@@ -1,6 +1,6 @@
 
 import {
-  AbstractUpdateDecoder, AbstractUpdateEncoder, Item, StructStore, Transaction // eslint-disable-line
+  AbstractType, AbstractUpdateDecoder, AbstractUpdateEncoder, Item, StructStore, Transaction // eslint-disable-line
 } from '../internals.js'
 
 import * as error from 'lib0/error.js'
@@ -66,7 +66,11 @@ export class ContentFormat {
    * @param {Transaction} transaction
    * @param {Item} item
    */
-  integrate (transaction, item) {}
+  integrate (transaction, item) {
+    // @todo searchmarker are currently unsupported for rich text documents
+    /** @type {AbstractType<any>} */ (item.parent)._searchMarker = null
+  }
+
   /**
    * @param {Transaction} transaction
    */

src/structs/Item.js

@@ -285,9 +285,31 @@ export class Item extends AbstractStruct {
      * @type {AbstractContent}
      */
     this.content = content
+    /**
+     * bit1: keep
+     * bit2: countable
+     * bit3: deleted
+     * bit4: mark - mark node as fast-search-marker
+     * @type {number} byte
+     */
     this.info = this.content.isCountable() ? binary.BIT2 : 0
   }
 
+  /**
+   * This is used to mark the item as an indexed fast-search marker
+   *
+   * @type {boolean}
+   */
+  set marker (isMarked) {
+    if (((this.info & binary.BIT4) > 0) !== isMarked) {
+      this.info ^= binary.BIT4
+    }
+  }
+
+  get marker () {
+    return (this.info & binary.BIT4) > 0
+  }
+
   /**
    * If true, do not garbage collect this Item.
    */