Add FreshRSS widget (#1377)

* feat: add FreshRSS widget

* refactor: revert credentialed.js

* refactor: custom proxy handler for FreshRSS

* refactor: cache the token as long as possible

During installation, the salt is generated and remains constant unless
the user re-installs the FreshRSS instance.

src/widgets/freshrss/component.jsx

@@ -0,0 +1,33 @@
+import { useTranslation } from "next-i18next";
+
+import Container from "components/services/widget/container";
+import Block from "components/services/widget/block";
+import useWidgetAPI from "utils/proxy/use-widget-api";
+
+export default function Component({ service }) {
+  const { t } = useTranslation();
+
+  const { widget } = service;
+
+  const { data: freshrssData, error: freshrssError } = useWidgetAPI(widget, "info");
+
+  if (freshrssError) {
+    return <Container error={freshrssError} />;
+  }
+
+  if (!freshrssData) {
+    return (
+      <Container service={service}>
+        <Block label="freshrss.unread" />
+        <Block label="freshrss.subscriptions" />
+      </Container>
+    );
+  }
+
+  return (
+    <Container service={service}>
+      <Block label="freshrss.unread" value={t("common.number", { value: freshrssData.unread })} />
+      <Block label="freshrss.subscriptions" value={t("common.number", { value: freshrssData.subscriptions })} />
+    </Container>
+  );
+}