Support SSE for source updates

This uses the Server Side Events added in Selfoss API 6.1.0 when calling GET /update
This change only supports the new response format but provides no change for the users.
The older versions are still supported.

shared/src/commonMain/kotlin/bou/amine/apps/readerforselfossv2/rest/SelfossApi.kt

@@ -19,6 +19,7 @@ import io.ktor.client.plugins.cookies.HttpCookies
 import io.ktor.client.plugins.logging.LogLevel
 import io.ktor.client.plugins.logging.Logger
 import io.ktor.client.plugins.logging.Logging
+import io.ktor.client.plugins.sse.SSE
 import io.ktor.client.request.get
 import io.ktor.client.request.headers
 import io.ktor.client.request.parameter
@@ -89,6 +90,7 @@ class SelfossApi(
                     }
                 }
             }
+            install(SSE)
             expectSuccess = false
         }
 
@@ -382,6 +384,10 @@ class SelfossApi(
                                 ),
                             ),
                         )
+                        append(
+                            HttpHeaders.Accept,
+                            "text/event-stream",
+                        )
                     }
                 }
             },