begin migrating graphiql-explorer into the repo, ts conversion

Author: acao

packages/graphiql-explorer/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "graphiql-explorer",
+  "version": "8.0.1",
+  "module": "dist/index.js",
+  "types": "types/index.d.ts"
+}