Large improvement to (model-dependent) token utilization

And update README.md

lib/data.ts

@@ -57,6 +57,7 @@ type ChatModelData = {
   description: string | JSX.Element;
   title: string;
   fullName: string; // seems unused
+  contextWindowSize: number,
 }
 
 export const ChatModels: { [key in ChatModelId]: ChatModelData } = {
@@ -64,10 +65,12 @@ export const ChatModels: { [key in ChatModelId]: ChatModelData } = {
     description: 'Most insightful, larger problems, but slow, expensive, and may be unavailable',
     title: 'GPT-4',
     fullName: 'GPT-4',
+    contextWindowSize: 8192,
   },
   'gpt-3.5-turbo': {
     description: 'A good balance between speed and insight',
     title: '3.5-Turbo',
     fullName: 'GPT-3.5 Turbo',
+    contextWindowSize: 4096,
   },
 };