Add framework-arduino-c61-skeleton-lib entry

Author: Jason2866

platform.json

@@ -47,6 +47,12 @@
       "owner": "espressif",
       "version": "https://github.com/pioarduino/platform-espressif32/releases/download/c2-skeleton/c2_8410210c9a_compile_skeleton.zip"
     },
+    "framework-arduino-c61-skeleton-lib": {
+      "type": "framework",
+      "optional": true,
+      "owner": "espressif",
+      "version": "https://github.com/pioarduino/platform-espressif32/releases/download/c61-skeleton/c61_d1e854920a_compile_skeleton.zip"
+    },
     "framework-espidf": {
       "type": "framework",
       "optional": true,