typescript: Migrate params-util.js to typescript.

app/renderer/js/utils/params-util.ts

@@ -1,15 +1,11 @@
 // This util function returns the page params if they're present else returns null
-function isPageParams() {
+export function isPageParams(): null | object {
 	let webpageParams = null;
 	try {
-		// eslint-disable-next-line no-undef, camelcase
+		// eslint-disable-next-line no-undef, @typescript-eslint/camelcase
 		webpageParams = page_params;
-	} catch (err) {
+	} catch (_) {
 		webpageParams = null;
 	}
 	return webpageParams;
 }
-
-module.exports = {
-	isPageParams
-};

typings.d.ts

@@ -4,5 +4,7 @@
 // are not supported
 declare module '*';
 
+declare var page_params: object;
+
 // since requestIdleCallback didn't make it into lib.dom.d.ts yet
 declare function requestIdleCallback(callback: Function, options?: object): void;