use a custom tinymce svelte component and other minor optimizations

.github/workflows/release.yaml

@@ -21,7 +21,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v3
         with:
-          go-version: '>=1.21.2'
+          go-version: '>=1.21.3'
 
       # This step usually is not needed because the /ui/dist is pregenerated locally
       # but its here to ensure that each release embeds the latest admin ui artifacts.