ts: Convert page_params module to TypeScript.

The plan for type annotating the page_params is to set it to
Record<string, unknown> for now and then annotate individual
properties on it as we use it in typescript modules.

static/js/global.d.ts

@@ -8,3 +8,7 @@ declare let zulip_test: any;
 interface JQuery {
     expectOne(): JQuery;
 }
+
+interface Window {
+    page_params_parse_time: number;
+}

static/js/page_params.ts

@@ -1,7 +1,7 @@
 import $ from "jquery";
 
 const t1 = performance.now();
-export const page_params = $("#page-params").remove().data("params");
+export const page_params: Record<string, unknown> = $("#page-params").remove().data("params");
 const t2 = performance.now();
 window.page_params_parse_time = t2 - t1;
 if (!page_params) {

tools/test-js-with-node

@@ -99,7 +99,7 @@ EXEMPT_FILES = {
     "static/js/notifications.js",
     "static/js/overlays.js",
     "static/js/padded_widget.js",
-    "static/js/page_params.js",
+    "static/js/page_params.ts",
     "static/js/navbar_alerts.js",
     "static/js/pm_list_dom.js",
     "static/js/poll_widget.js",