docs: add root README for releases (#11)

Co-authored-by: Codex <codex@local>

Author: skulidropek

README.md

@@ -0,0 +1,36 @@
+# openapi-effect
+
+Drop-in replacement for `openapi-fetch` with an opt-in Effect API.
+
+## Install
+
+```bash
+pnpm add @prover-coder-ai/openapi-effect
+```
+
+## Usage (Promise API)
+
+This package re-exports `openapi-fetch`, so most code can be migrated by changing only the import.
+
+```ts
+import createClient from "@prover-coder-ai/openapi-effect"
+import type { paths } from "./openapi"
+
+const client = createClient<paths>({ baseUrl: "https://api.example.com" })
+
+const { data, error } = await client.GET("/pets", {
+  params: { query: { limit: 10 } }
+})
+
+if (error) {
+  // handle error
+}
+```
+
+## Usage (Effect API)
+
+Effect-based client is available as an opt-in API.
+
+```ts
+import { createClientEffect, FetchHttpClient } from "@prover-coder-ai/openapi-effect"
+```