Add Hebrew Calendar API

Adds hebcal.com API to the list

README.md

@@ -124,6 +124,7 @@ API | Description | Auth | HTTPS | Link |
 | Church Calendar | Catholic liturgical calendar | No | No | [Go!](http://calapi.inadiutorium.cz/) |
 | Czech Namedays Calendar | Lookup for a name and returns nameday date | No | No | [Go!](http://svatky.adresa.info/) |
 | Google Calendar | Display, create and modify Google calendar events | `OAuth` | Yes | [Go!](https://developers.google.com/google-apps/calendar/) |
+| Hebrew Calendar | Convert between Gregarian and Hebrew, fetch Shabbat and Holiday times, etc. | No | No | [Go!](https://www.hebcal.com/home/developer-apis) |
 | Holidays | Historical data regarding holidays | `apiKey` | Yes | [Go!](https://holidayapi.com/) |
 | LectServe | Protestant liturgical calendar | No | No | [Go!](http://www.lectserve.com) |
 | Non-Working Days | Database of ICS files for non working days | No | Yes | [Go!](https://github.com/gadael/icsdb) |