themes: update Sakuras Simple Sidebar theme (#305)

Author: SakuraMeadows

themes.json

@@ -2124,7 +2124,7 @@
     "title": "Sakuras Simple Sidebar",
     "link": "https://github.com/SakuraMeadows/Sakuras-Simple-Sidebar",
     "description": "A simple Firefox theme using Sidebery sidebar.",
-    "image": "https://camo.githubusercontent.com/c4bcbd77078ad964f88351097b39a5689071ee1115b155e9ab2a6fe215193907/68747470733a2f2f692e696d6775722e636f6d2f686f4f696e596b2e706e67",
+    "image": "https://github.com/SakuraMeadows/Sakuras-Simple-Sidebar/blob/39908072a7fe102f91658d5df73ce24ad24d6290/page%20assets/SakurasSimpleSidebarExample.gif",
     "tags": [
       "SakuraMeadows",
       "theme type: dark",
@@ -2140,4 +2140,4 @@
     "stargazers_count": 3,
     "avatar": "https://avatars.githubusercontent.com/u/93335748?v=4"
   }
-]
+]