Fix internal TS issues with latest Node Buffer types

Author: pimterry

src/rules/matchers.ts

@@ -403,8 +403,10 @@ export class MultipartFormDataMatcher extends Serializable implements RequestMat
         const parsedBody = multipart.parse(await request.body.asDecodedBuffer(), boundary[1]);
 
         return this.matchConditions.every((condition) => {
-            const expectedContent = condition.content
-                ? Buffer.from(condition.content)
+            const expectedContent = typeof condition.content === 'string'
+                    ? Buffer.from(condition.content, "utf8")
+                : condition.content
+                    ? Buffer.from(condition.content)
                 : undefined;
 
             return parsedBody.some((part) =>

src/rules/requests/request-handlers.ts

@@ -193,7 +193,10 @@ async function writeResponseFromCallback(
         // RawBody takes priority if both are set (useful for backward compat) but if not then
         // the body is automatically encoded to match the content-encoding header.
         result.rawBody = await encodeBodyBuffer(
-            Buffer.from(result.body),
+            // Separate string case mostly required due to TS type issues:
+            typeof result.body === 'string'
+                ? Buffer.from(result.body, "utf8")
+                : Buffer.from(result.body),
             result.headers ?? {}
         );
     }