feat: make og images an emitter to properly await image generation (#1826)

* checkpoint

* make emitters async generators

* fix

* custom font spec

* replace spinner, use disk cache for fonts

* use readline instead

* make og images look nice

quartz/plugins/emitters/index.ts

@@ -8,3 +8,4 @@ export { Static } from "./static"
 export { ComponentResources } from "./componentResources"
 export { NotFoundPage } from "./404"
 export { CNAME } from "./cname"
+export { CustomOgImages } from "./ogImage"