Add missing types

@@ -150,6 +150,7 @@ The Firebase AI Web SDK.
 | [BackendType](./ai.md#backendtype) | Type alias representing valid backend types. It can be either <code>'VERTEX_AI'</code> or <code>'GOOGLE_AI'</code>. |
 | [InferenceMode](./ai.md#inferencemode) | Determines whether inference happens on-device or in-cloud. |
 | [LanguageModelInitialPrompts](./ai.md#languagemodelinitialprompts) | |
+| [LanguageModelMessageRole](./ai.md#languagemodelmessagerole) | |
 | [LanguageModelMessageType](./ai.md#languagemodelmessagetype) | |
 | [Part](./ai.md#part) | Content part - includes text, image/video, or function call/response part types. |
 | [ResponseModality](./ai.md#responsemodality) | <b><i>(Public Preview)</i></b> Generation modalities to be returned in generation responses. |
@@ -389,6 +390,14 @@ export type InferenceMode = 'prefer_on_device' | 'only_on_device' | 'only_in_clo
 export type LanguageModelInitialPrompts = LanguageModelMessage[] | LanguageModelMessageShorthand[];
 ```
 
+## LanguageModelMessageRole
+
+<b>Signature:</b>
+
+```typescript
+export type LanguageModelMessageRole = 'system' | 'user' | 'assistant';
+```
+
 ## LanguageModelMessageType
 
 <b>Signature:</b>

@@ -30,6 +30,7 @@ export {
 LanguageModelInitialPrompts,
 LanguageModelMessage,
 LanguageModelMessageContent,
+LanguageModelMessageRole,
 LanguageModelMessageShorthand,
 LanguageModelMessageType
 } from './language-model';