Fix typedoc entrypoint

The entrypoint referred to was removed in commit 848dc3c
diff --git a/typedoc.json b/typedoc.json
index d2aeb6e..bd8a5e1 100644
--- a/typedoc.json
+++ b/typedoc.json
@@ -1,3 +1,3 @@
 {
-  "entryPoints": ["packages/apache-annotator/src/index.ts"]
+  "entryPoints": ["packages/apache-annotator/src/"]
 }