[gimp-web] content: add GIMP 2.99.8 release for macOS!

[Jehan <jehanp src gnome org>]

commit 341e847208d2e2da9222d3a83c4e0192176cd4ff
Author: Jehan <jehan girinstud io>
Date:   Sat Dec 4 19:29:22 2021 +0100

    content: add GIMP 2.99.8 release for macOS!
    
    Woohoo! The first DMG for the 2.99 dev series!

 content/gimp_versions.json | 11 +++++++++++
 1 file changed, 11 insertions(+)
---
diff --git a/content/gimp_versions.json b/content/gimp_versions.json
index 829db8f0..dcca706c 100644
--- a/content/gimp_versions.json
+++ b/content/gimp_versions.json
@@ -573,6 +573,17 @@
                     "min-support": "Windows 7",
                     "build-id": "Unknown"
                 }
+            ],
+            "macos": [
+                {
+                    "date": "2021-12-04",
+                    "filename": "gimp-2.99.8-x86_64.dmg",
+                    "sha512": 
"b6c285a98a7d7b77b5663bf94d5edd4753558438fa32fa2f73029f6c215107e50eae8b8067a53f3204edd212bdf28fe5dbdf39f88f80147695334218712882e1",
+                    "sha256": "b7636a00f5103fc3df3627f01f9946285a040ec84b68df1f332f9fdc68f43641",
+                    "min-support": "macOS 10.12 Sierra",
+                    "build-id": "org.gimp.GIMP_official",
+                    "comment": "First development release for macOS in 2.99 series"
+                }
             ]
         },
         {