chore: add accessToken to docs

Author: guabu

packages/auth0-auth-js/EXAMPLES.md

@@ -350,8 +350,11 @@ const tokenResponseForGoogle = await authClient.getTokenForConnection({ connecti
 ```
 
 - `refreshToken`: The refresh token to use to retrieve the access token.
+- `accessToken`: The access token to use to retrieve the access token.
 - `connection`: The connection for which an access token should be retrieved, e.g. `google-oauth2` for Google.
-- `loginHint`: Optional login hint to inform which connection account to use, can be useful when multiple accounts for the connection exist for the same user. 
+- `loginHint`: Optional login hint to inform which connection account to use, can be useful when multiple accounts for the connection exist for the same user.
+
+Either the `refreshToken` or `accessToken` parameter can be specified, but not both.
 
 Note that, when using `google-oauth2`, it's required to set both `authorizationParams.access_type` and `authorizationParams.prompt` to `offline` and `consent` respectively when building the authorization URL.