refactor: move emit from callback to helper file function (#704)

* Change emit from callback to helpers file function

* Update docs, remove commented code, improve type sig

quartz/plugins/types.ts

@@ -36,19 +36,6 @@ export type QuartzEmitterPlugin<Options extends OptionType = undefined> = (
 ) => QuartzEmitterPluginInstance
 export type QuartzEmitterPluginInstance = {
   name: string
-  emit(
-    ctx: BuildCtx,
-    content: ProcessedContent[],
-    resources: StaticResources,
-    emitCallback: EmitCallback,
-  ): Promise<FilePath[]>
+  emit(ctx: BuildCtx, content: ProcessedContent[], resources: StaticResources): Promise<FilePath[]>
   getQuartzComponents(ctx: BuildCtx): QuartzComponent[]
 }
-
-export interface EmitOptions {
-  slug: FullSlug
-  ext: `.${string}` | ""
-  content: string
-}
-
-export type EmitCallback = (data: EmitOptions) => Promise<FilePath>