Add OpenAPI clients and schema as release assets

!66 (merged) added automatic generation of OpenAPI clients. #24 (closed) and #23 (closed) require that the clients be added as release assets but that functionality, at time of merging, was broken in release-it (Upstream issue).

The upstream release of release-it now includes a fix for the issue we were seeing.

This issue tracks adding the remaining functionality so that #24 (closed) and #23 (closed) can be unblocked which should be trivial using config similar to:

diff --git a/.release-it.json b/.release-it.json
index be06e0f..879351b 100644
--- a/.release-it.json
+++ b/.release-it.json
@@ -5,7 +5,11 @@
   "gitlab": {
     "release": true,
     "releaseName": "${version}",
-    "useIdsForUrls": true
+    "useIdsForUrls": true,
+    "assets": [
+      "openapi.yaml",
+      "clients/**"
+    ]
   },
   "plugins": {
     "@release-it/conventional-changelog": {