Add calendar file (#107)

* Cal file

* Update Calendar/README.md

---------

Co-authored-by: margaretkennedy <82049573+margaretkennedy@users.noreply.github.com>

Calendar/CompanyY_2024.calendar

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+<calendar>
+    <name>CompanyY_2024</name>
+    <timeZone>America/New_York</timeZone>
+    <language>en</language>
+    <country>US</country>
+    <firstValidDate>2024-01-01</firstValidDate>
+    <lastValidDate>2024-12-31</lastValidDate>
+    <description>
+        Company Y calendar for the year 2024.
+        Company Y uses two business periods instead of one.
+        The periods are separated by a one hour lunch break.
+        This calendar file defines standard business hours, weekends, and holidays.
+    </description>
+        <default>
+        <businessTime><open>08:00</open><close>12:00</close><open>13:00</open><close>17:00</close></businessTime>
+        <weekend>Saturday</weekend>
+        <weekend>Sunday</weekend>
+    </default>
+    <holiday>
+        <date>2024-01-01</date>
+    </holiday>
+    <holiday>
+        <date>2024-01-15</date>
+    </holiday>
+    <holiday>
+        <date>2024-02-19</date>
+    </holiday>
+    <holiday>
+        <date>2024-03-29</date>
+    </holiday>
+    <holiday>
+        <date>2024-04-01</date>
+        <businessTime><open>08:00</open><close>12:00</close></businessTime>
+    </holiday>
+    <holiday>
+        <date>2024-05-27</date>
+    </holiday>
+    <holiday>
+        <date>2024-07-04</date>
+    </holiday>
+    <holiday>
+        <date>2024-09-02</date>
+    </holiday>
+    <holiday>
+        <date>2024-10-31</date>
+        <businessTime><open>08:00</open><close>12:00</close></businessTime>
+    </holiday>
+    <holiday>
+        <date>2024-11-28</date>
+    </holiday>
+    <holiday>
+        <date>2024-11-29</date>
+    </holiday>
+    <holiday>
+        <date>2024-12-25</date>
+    </holiday>
+    <holiday>
+        <date>2024-12-26</date>
+    </holiday>
+</calendar>

Calendar/README.md

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+# Calendar
+
+This folder contains a calendar file in XML format.
+
+## Table of contents
+
+`CompanyY_2024.calendar`: A calendar file for a hypothetical company, `Company Y`, in XML format.
+
+## Calendar file
+
+A calendar file can be used by Deephaven's calendar API to add a custom calendar to the list of available calendars. This calendar file is used in Deephaven's documentation to show how this can be done.
+
+## Use a custom calendar
+
+Here's an example of the documentation for using a custom calendar:
+
+```python
+from deephaven.calendar import add_calendar, calendar, calendar_names
+
+add_calendar("https://media.githubusercontent.com/media/deephaven/examples/main/Calendar/CompanyY_2024.calendar")
+
+print(calendar_names())
+
+company_y_cal_2024 = calendar("CompanyY_2024")
+```