Update accent_circonflexe.json

Allow combining circumflex \u0302 for Cyrillic vowels, enabling users to express themselves accurately.

ја сам са̂м = I am alone
ја сам сам = I am am

да = yes
да̂ = give

код = at
ко̂д = code

Similar to #437 for aigo.

srcs/compose/accent_circonflexe.json

@@ -9,5 +9,10 @@
   "o": "ô",
   "ŝ": "ŝ",
   "u": "û",
-  "z": "ẑ"
+  "z": "ẑ",
+  "а": "а\u0302",
+  "е": "е\u0302",
+  "и": "и\u0302",
+  "о": "о\u0302",
+  "у": "у\u0302"
 }