[calls] call: Document call states

[Evangelos Ribeiro Tzaras <devrtz src gnome org>]

commit 09688a1e80432698d36cccc10496b1f8835cf252
Author: Evangelos Ribeiro Tzaras <devrtz fortysixandtwo eu>
Date:   Wed Jun 22 23:04:30 2022 +0200

    call: Document call states

 src/calls-call.h | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/src/calls-call.h b/src/calls-call.h
index 9b6f0b16..946f6e93 100644
--- a/src/calls-call.h
+++ b/src/calls-call.h
@@ -32,6 +32,16 @@ G_BEGIN_DECLS
 
 G_DECLARE_DERIVABLE_TYPE (CallsCall, calls_call, CALLS, CALL, GObject)
 
+/**
+ * CallsCallState:
+ * @CALLS_CALL_STATE_UNKNOWN: Call state unknown
+ * @CALLS_CALL_STATE_ACTIVE: Call is active
+ * @CALLS_CALL_STATE_HELD: Call is being held
+ * @CALLS_CALL_STATE_DIALING: Outgoing call being established
+ * @CALLS_CALL_STATE_ALERTING: Remote party is being alerted
+ * @CALLS_CALL_STATE_INCOMING: New incoming call
+ * @CALLS_CALL_STATE_DISCONNECTED: Call was successfully terminated
+ */
 typedef enum {
   CALLS_CALL_STATE_UNKNOWN = 0,
   CALLS_CALL_STATE_ACTIVE,