Fix ETag wording in docs/index.md (#18)

* Fix ETag wording in docs/index.md key features section

ETag is a response header sent by the server; the client sends
If-None-Match. Rephrased to: 'sends If-None-Match with the cached ETag'
to avoid implying ETag is a request header.

Addresses Copilot review comment on #14.

* Apply Copilot suggestion: format ETag as code in index.md

Author: ronaldvdmeer

docs/index.md

@@ -11,7 +11,7 @@ Async Python client library for the [Eve Online ESI API](https://esi.evetech.net
 
 ## Key features
 
-- **Two-layer caching** — respects the ESI `Expires` header to skip HTTP requests entirely within the cache window, and sends `If-None-Match` / ETag headers so unchanged responses return HTTP 304 without a response body. Both layers work automatically with no configuration required.
+- **Two-layer caching** — respects the ESI `Expires` header to skip HTTP requests entirely within the cache window, and sends `If-None-Match` with the cached `ETag` so unchanged responses return HTTP 304 without a response body. Both layers work automatically with no configuration required.
 - **Automatic pagination** — paginated endpoints (`async_get_wallet_journal()`, `async_get_contacts()`, `async_get_killmails()`) fetch all pages transparently and return a single combined list.
 - **23 endpoints** covering public and auth-gated ESI resources — see [Endpoints](endpoints.md) for the full list.
 - **Typed models** — all responses are frozen dataclasses with full type annotations and PEP 561 `py.typed` marker.