Add API Console links to the REST API pages.

- Add links and other small edits to the "REST API usage" page.
- Hack around a bit to add a custom header to the generated "REST API reference" page.

api/body.hbs

@@ -2,6 +2,9 @@
 is_api: true
 comment: spaces in body are important, do not remove without checking result.
 toc:
+  -
+    title: "Grist API Reference"
+    url: "#_top"
   -
     title: "Authentication"
     url: "#section/Authentication"
@@ -35,9 +38,17 @@ toc:
     url: "#tag/data"
 ---
 
+<a name="_top"></a>
+<div markdown class="api-header">
+
+# Grist API Reference
+
+REST API for manipulating documents, workspaces, and team sites.
+
+- [API Usage](rest-api.md) is an introduction to using the API.
+- [API Console](https://docs.getgrist.com/apiconsole) allows you to make API calls from the browser.
+</div>
 
 <div>
 {{{redocHTML}}}
 </div>
-
-

api/head.hbs

@@ -13,7 +13,13 @@
    display: none;
  }
  .api-info {
-   padding-top: 20px !important;
+   display: none;
+ }
+ .api-header {
+   padding: 20px 40px 0 40px;
+ }
+ .api-header a {
+   color: var(--color-link);
  }
 </style>
 {% raw %}{{{redocHead}}}{% endraw %}