OpenAPI: Add link to our "Data Access Policy" in the description (#10613)

Author: Turbo87

src/openapi.rs

@@ -12,6 +12,10 @@ This document describes the API used by the crates.io website, cargo
 client, and other third-party tools to interact with the crates.io
 registry.
 
+Before using this API, please read the
+[crates.io data access policy](https://crates.io/data-access) and ensure
+that your use of the API complies with the policy.
+
 __The API is under active development and may change at any time__,
 though we will try to avoid breaking changes where possible.
 

src/snapshots/crates_io__openapi__tests__openapi_snapshot.snap

@@ -24,7 +24,7 @@ expression: response.json()
       "email": "[email protected]",
       "name": "the crates.io team"
     },
-    "description": "\n__Experimental API documentation for the [crates.io](https://crates.io/)\npackage registry.__\n\nThis document describes the API used by the crates.io website, cargo\nclient, and other third-party tools to interact with the crates.io\nregistry.\n\n__The API is under active development and may change at any time__,\nthough we will try to avoid breaking changes where possible.\n\nSome parts of the API follow the \"Registry Web API\" spec documented\nat <https://doc.rust-lang.org/cargo/reference/registry-web-api.html>\nand can be considered stable.\n\nMost parts of the API do not require authentication. The endpoints\nthat do require authentication are marked as such in the documentation,\nwith some requiring cookie authentication (usable only by the web UI)\nand others requiring API token authentication (usable by cargo and\nother clients).\n",
+    "description": "\n__Experimental API documentation for the [crates.io](https://crates.io/)\npackage registry.__\n\nThis document describes the API used by the crates.io website, cargo\nclient, and other third-party tools to interact with the crates.io\nregistry.\n\nBefore using this API, please read the\n[crates.io data access policy](https://crates.io/data-access) and ensure\nthat your use of the API complies with the policy.\n\n__The API is under active development and may change at any time__,\nthough we will try to avoid breaking changes where possible.\n\nSome parts of the API follow the \"Registry Web API\" spec documented\nat <https://doc.rust-lang.org/cargo/reference/registry-web-api.html>\nand can be considered stable.\n\nMost parts of the API do not require authentication. The endpoints\nthat do require authentication are marked as such in the documentation,\nwith some requiring cookie authentication (usable only by the web UI)\nand others requiring API token authentication (usable by cargo and\nother clients).\n",
     "license": {
       "name": "MIT OR Apache-2.0",
       "url": "https://github.com/rust-lang/crates.io/blob/main/README.md#%EF%B8%8F-license"