[gimp-web] Add a warning about 2.99.4 export broken on Windows.

[Jehan <jehanp src gnome org>]

commit 657a8972c7321067e3835a95fdcb46e8db73d326
Author: Jehan <jehan girinstud io>
Date:   Mon Mar 8 16:22:18 2021 +0100

    Add a warning about 2.99.4 export broken on Windows.
    
    See also gimp reports 6142 and 6548. It's clearly not an ideal testbed,
    better tell about this particular very bad bug.

 content/gimp_versions.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/content/gimp_versions.json b/content/gimp_versions.json
index 70573d85..3798be17 100644
--- a/content/gimp_versions.json
+++ b/content/gimp_versions.json
@@ -479,7 +479,7 @@
                     "min-support": "Windows 7",
                     "build-id": "org.gimp.GIMP_official",
                     "revision": 1,
-                    "comment": "Update: adds the Paint Select tool in the Playground preferences"
+                    "comment": "<strong>Warning</strong>: JPEG, PNG, TIFF and FLI export are not 
working!<br/>Update: adds the Paint Select tool in the Playground preferences"
                  },
                  {
                     "date": "2020-12-25",