docs: minor syntax highlight fix on the README (#1549)

README.md

@@ -236,7 +236,7 @@ You can use all of the following options with standalone version on <redoc> tag
 * `hideSchemaPattern` - if set, the pattern is not shown in the schema.
 * `hideSingleRequestSampleTab` - do not show the request sample tab for requests with only one sample.
 * `expandSingleSchemaField` - automatically expand single field in a schema
-* `jsonSampleExpandLevel` - set the default expand level for JSON payload samples (responses and request body). Special value 'all' expands all levels. The default value is `2`.
+* `jsonSampleExpandLevel` - set the default expand level for JSON payload samples (responses and request body). Special value `"all"` expands all levels. The default value is `2`.
 * `hideSchemaTitles` - do not display schema `title` next to to the type
 * `simpleOneOfTypeLabel` - show only unique oneOf types in the label without titles
 * `lazyRendering` - _Not implemented yet_ ~~if set, enables lazy rendering mode in ReDoc. This mode is useful for APIs with big number of operations (e.g. > 50). In this mode ReDoc shows initial screen ASAP and then renders the rest operations asynchronously while showing progress bar on the top. Check out the [demo](\\redocly.github.io/redoc) for the example.~~