Update azure-active-directory-b2c.md (#609)

Make it very explicit that the redirectUrl must end with a slash

Author: badsyntax

docs/config-examples/azure-active-directory-b2c.md

@@ -6,7 +6,7 @@ Detailed documentation [here](https://docs.microsoft.com/en-us/azure/active-dire
 const config = {
   issuer: 'https://<TENANT_NAME>.b2clogin.com/<TENANT_NAME>.onmicrosoft.com/<USER_FLOW_NAME>/v2.0',
   clientId: '<APPLICATION_ID>',
-  redirectUrl: 'com.myapp://redirect/url/',
+  redirectUrl: 'com.myapp://redirect/url/', // the redirectUrl must end with a slash
   scopes: ['openid', 'offline_access']
 };
 
@@ -17,4 +17,4 @@ const authState = await authorize(config);
 const refreshedState = await refresh(config, {
   refreshToken: authState.refreshToken,
 });
-```
+```