docs: add 'maxDisplayedEnumValues' option to docs (Redocly#1421)

README.md

@@ -226,6 +226,7 @@ You can use all of the following options with standalone version on <redoc> tag
 * `disableSearch` - disable search indexing and search box.
 * `expandDefaultServerVariables` - enable expanding default server variables, default `false`.
 * `expandResponses` - specify which responses to expand by default by response codes. Values should be passed as comma-separated list without spaces e.g. `expandResponses="200,201"`. Special value `"all"` expands all responses by default. Be careful: this option can slow-down documentation rendering time.
+* `maxDisplayedEnumValues` - display only specified number of enum values. hide rest values under spoiler.
 * `hideDownloadButton` - do not show "Download" spec button. **THIS DOESN'T MAKE YOUR SPEC PRIVATE**, it just hides the button.
 * `hideHostname` - if set, the protocol and hostname is not shown in the operation definition.
 * `hideLoading` - do not show loading animation. Useful for small docs.