Use resolve for homeserver, fixing trailing slash issues

.github/workflows/windows.yml

@@ -26,7 +26,7 @@ jobs:
         with:
           go-version-file: gomuks/go.mod
 
-      - name: Do go build
+      - name: Go build
         run: |
           cd gomuks/pkg/ffi
           go build -tags goolm -o ../../../libgomuks.dll -buildmode=c-shared

lib/helpers/extensions/mxc_to_https.dart

@@ -1,4 +1,5 @@
 extension MxcToHttps on Uri {
-  Uri mxcToHttps(String homeserver) =>
-      Uri.parse("${homeserver}_matrix/client/v1/media/download/$host$path");
+  Uri mxcToHttps(String homeserver) => Uri.parse(
+    homeserver,
+  ).resolve("_matrix/client/v1/media/download/$host$path");
 }