🔧(backend) add LiveKit API secret/key pair in Django settings

When starting the LiveKit server using the '--dev' option, the server uses
defaults secret/key pair according to the documentation.

Make sure the Django settings and de facto the environment variable match
these defaults.

Please have a look at the documentation page here:
https://docs.livekit.io/home/self-hosting/local/

env.d/development/common.dist

@@ -39,3 +39,7 @@ LOGOUT_REDIRECT_URL=http://localhost:3000
 
 OIDC_REDIRECT_ALLOWED_HOSTS=["http://localhost:8083", "http://localhost:3000"]
 OIDC_AUTH_REQUEST_EXTRA_PARAMS={"acr_values": "eidas1"}
+
+# Livekit Token settings
+LIVEKIT_API_SECRET="secret"
+LIVEKIT_API_KEY="devkey"