Bugfix/increase tokens (#132)

* feat(api.ts): add support for OPENAI_MAX_TOKENS environment variable
feat(config.ts): add OPENAI_MAX_TOKENS to CONFIG_KEYS and configValidators

* 2.0.2

* 2.0.3

* docs(README.md): add GPT-4 usage instructions and mention the cost difference compared to GPT-3.5-turbo

---------

Co-authored-by: di-sukharev <dim.sukharev@gmail.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "opencommit",
-  "version": "2.0.1",
+  "version": "2.0.3",
   "description": "GPT CLI to auto-generate impressive commits in 1 second. Killing lame commits with AI 🤯🔫",
   "keywords": [
     "git",