docs: update info about WASM web-demo example

czv-wasm/examples/web-demo/script.ts

@@ -0,0 +1,34 @@
+const progress = document.getElementById("progress");
+
+import init, * as czv from "../../pkg/czv.js";
+// Must run `await init()` or `initSync()` first for web use
+await init();
+
+const fileReader = new FileReader();
+
+fileReader.onloadstart = () => {
+    if (progress) progress.style.display = "block";
+};
+
+fileReader.onloadend = () => {
+    const rowCountElement = document.getElementById("row-count");
+    const columnCountElement = document.getElementById("column-count");
+    if (rowCountElement)
+        rowCountElement.innerText = String(
+            czv.rowCount({
+                file_data: fileReader.result as string,
+            })
+        );
+    if (columnCountElement)
+        columnCountElement.innerText = String(
+            czv.columnCount({ file_data: fileReader.result as string })
+        );
+    if (progress) progress.style.display = "none";
+};
+
+const input = document.getElementById("upload");
+if (input)
+    input.addEventListener("change", () => {
+        // @ts-ignore
+        fileReader.readAsText(input.files[0]);
+    });