fix(assets): pdf page linking support. (jackyzha0#1025)

* github-slugger pdf workaround

* Skip sluggifying on pdf file extension

* Account for pdf files without anchor

* Address feedback

quartz/util/path.ts

@@ -168,6 +168,9 @@ export function resolveRelative(current: FullSlug, target: FullSlug | SimpleSlug
 
 export function splitAnchor(link: string): [string, string] {
   let [fp, anchor] = link.split("#", 2)
+  if (fp.endsWith(".pdf")) {
+    return [fp, anchor === undefined ? "" : `#${anchor}`]
+  }
   anchor = anchor === undefined ? "" : "#" + slugAnchor(anchor)
   return [fp, anchor]
 }