Fix strange TypeDoc regression in Custom Directives generated API. (#1098)

* Fix strange TypeDoc regression in Custom Directives API.

Somehow TypeDoc no longer recognizes the type for `ReadonlyArray`.
This is a hack just for this page.

* Add TODO with github issue.

Author: AndrewJakubowicz

packages/lit-dev-content/site/_includes/api.html

@@ -143,6 +143,10 @@
     {%- elif t.name and t.name !== '__type' -%}
       {{- t.name -}}
 
+    {%- elif page.url.includes("api/custom-directives") -%}
+      <!-- TODO(https://github.com/lit/lit.dev/issues/1099) -->
+      ReadonlyArray&lt;string>
+
     {%- else -%}
       TODO
       {# {{ t | dump }} #}