feat: add pdfpc-file metadata in typst directly

utils/pdfpc.typ

@@ -1,3 +1,54 @@
+#let pdfpc-file = {
+  locate(loc => {
+    let arr = query(<pdfpc>, loc).map(it => it.value)
+    let (config, ..slides) = arr.split((t: "NewSlide"))
+    let pdfpc = (
+      pdfpcFormat: 2,
+      disableMarkdown: false,
+    )
+    for item in config {
+      pdfpc.insert(lower(item.t.at(0)) + item.t.slice(1), item.v)
+    }
+    let pages = ()
+    for slide in slides {
+      let page = (
+        idx: 0,
+        label: 1,
+        overlay: 0,
+        forcedOverlay: false,
+        hidden: false,
+      )
+      for item in slide {
+        if item.t == "Idx" {
+          page.idx = item.v
+        } else if item.t == "LogicalSlide" {
+          page.label = item.v
+        } else if item.t == "Overlay" {
+          page.overlay = item.v
+          page.forcedOverlay = item.v > 0
+        } else if item.t == "HiddenSlide" {
+          page.hidden = true
+        } else if item.t == "SaveSlide" {
+          if "savedSlide" not in pdfpc {
+            pdfpc.savedSlide = page.label - 1
+          }
+        } else if item.t == "EndSlide" {
+          if "endSlide" not in pdfpc {
+            pdfpc.endSlide = page.label - 1
+          }
+        } else if item.t == "Note" {
+          page.note = item.v
+        } else {
+          pdfpc.insert(lower(item.t.at(0)) + item.t.slice(1), item.v)
+        }
+      }
+      pages.push(page)
+    }
+    pdfpc.insert("pages", pages)
+    [#metadata(pdfpc)<pdfpc-file>]
+  })
+}
+
 #let speaker-note(text) = {
   let text = if type(text) == "string" {
     text
@@ -91,4 +142,7 @@
 
     [ #metadata((t: "DefaultTransition", v: transition-str)) <pdfpc> ]
   }
+
+  // add a <pdfpc-file> metadata to generate json-based pdfpc file
+  pdfpc-file
 }