add calendars to the component guide (#10147)

frontend/src/metabase/components/Calendar.info.js

+import React from "react";
+import moment from "moment";
+import Calendar from "./Calendar";
+
+export const component = Calendar;
+
+export const description = `For when gregorian time is your need, a calendar is your friend indeed`;
+
+const onChange = () => ({});
+
+export const examples = {
+  default: <Calendar onChange={onChange} />,
+  "With a selected date": <Calendar onChange={onChange} selected={moment()} />,
+  "With a date range": (
+    <Calendar
+      selected={moment()}
+      selectedEnd={moment().add(10, "days")}
+      onChange={onChange}
+    />
+  ),
+  "Dual with a date range": (
+    <Calendar
+      isDual
+      selected={moment()}
+      selectedEnd={moment().add(1, "month")}
+      onChange={onChange}
+    />
+  ),
+};