Add model aliases

Author: OriPekelman

lib/ruby_llm/aliases.json

@@ -46,5 +46,14 @@
   },
   "o3-mini": {
     "openai": "o3-mini-2025-01-31"
+  },
+  "mistral-medium": {
+    "mistral": "mistral-medium-latest"
+  },
+  "mistral-large": {
+    "mistral": "mistral-large-latest"
+  },
+  "mistral-small": {
+    "mistral": "mistral-small-latest"
   }
 }