add support for serving client+server well-known and /client/server.json endpoints from conduwuit

the last endpoint is a non-standard health check endpoint used by at
least Element Web as a weird way to determine if syncv3 is available

there can also be some valid use-cases for serving well-knowns from the
application itself

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/service/globals/mod.rs

@@ -509,6 +509,10 @@ impl Service<'_> {
         &self.config.well_known_client
     }
 
+    pub fn well_known_server(&self) -> &Option<String> {
+        &self.config.well_known_server
+    }
+
     pub fn unix_socket_path(&self) -> &Option<PathBuf> {
         &self.config.unix_socket_path
     }