Add matchedSubstrings to spellCheck interface (#192)

Raiden needs access](https://yext.slack.com/archives/C03NQ9X8ACB/p1658505872261039) to `matchedSubstrings` from the spellCheck part of the Search API response.  Since changing `correctedQuery` from a string to an object would be a breaking change, we added a new property to the spellCheck interface that holds the `matchedSubstrings`.  `matchedSubstrings` was also added to the Core response when the spellCheck object is created in `createSpellCheck`.

J=SLAP-2274
TEST=manual

It was verified that when spellCheck was provided in the Core response, that `matchedSubstrings` was also provided as its own property.

docs/search-core.spellcheck.matchedsubstrings.md

@@ -0,0 +1,16 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [@yext/search-core](./search-core.md) &gt; [SpellCheck](./search-core.spellcheck.md) &gt; [matchedSubstrings](./search-core.spellcheck.matchedsubstrings.md)
+
+## SpellCheck.matchedSubstrings property
+
+An array of substring matches which correspond to the highlighting. Offset indicates the index of the match, and the length indicates the number of characters of the match.
+
+<b>Signature:</b>
+
+```typescript
+matchedSubstrings: {
+        length: number;
+        offset: number;
+    }[];
+```

docs/search-core.spellcheck.md

@@ -17,6 +17,7 @@ export interface SpellCheck
 |  Property | Type | Description |
 |  --- | --- | --- |
 |  [correctedQuery](./search-core.spellcheck.correctedquery.md) | string | The corrected version of the originalQuery. |
+|  [matchedSubstrings](./search-core.spellcheck.matchedsubstrings.md) | { length: number; offset: number; }\[\] | An array of substring matches which correspond to the highlighting. Offset indicates the index of the match, and the length indicates the number of characters of the match. |
 |  [originalQuery](./search-core.spellcheck.originalquery.md) | string | The query that was input into the spell checker. |
 |  [type](./search-core.spellcheck.type.md) | [SpellCheckType](./search-core.spellchecktype.md) | The type of spell check. |
 

etc/search-core.api.md

@@ -492,6 +492,10 @@ export enum Source {
 // @public
 export interface SpellCheck {
     correctedQuery: string;
+    matchedSubstrings: {
+        length: number;
+        offset: number;
+    }[];
     originalQuery: string;
     type: SpellCheckType;
 }

src/models/searchservice/response/SpellCheck.ts

@@ -9,7 +9,15 @@ export interface SpellCheck {
   /** The corrected version of the originalQuery. */
   correctedQuery: string,
   /** The type of spell check. */
-  type: SpellCheckType
+  type: SpellCheckType,
+  /**
+   * An array of substring matches which correspond to the highlighting.
+   * Offset indicates the index of the match, and the length indicates the number of characters of the match.
+  */
+  matchedSubstrings: {
+    length: number,
+    offset: number
+  }[]
 }
 
 /**

src/transformers/searchservice/createSpellCheck.ts

@@ -5,5 +5,6 @@ export function createSpellCheck(data: any): SpellCheck {
     originalQuery: data.originalQuery,
     correctedQuery: data.correctedQuery.value,
     type: data.type,
+    matchedSubstrings: data.correctedQuery.matchedSubstrings
   };
 }