Add Sri Lanka holidays

README.rst

@@ -146,7 +146,7 @@ Available Countries
 .. _ISO 639-1 code: https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes
 .. _ISO 639-2 code: https://en.wikipedia.org/wiki/List_of_ISO_639-2_codes
 
-We currently support 156 country codes. The standard way to refer to a country
+We currently support 157 country codes. The standard way to refer to a country
 is by using its `ISO 3166-1 alpha-2 code`_, the same used for domain names, and
 for a subdivision its `ISO 3166-2 code`_. Some countries have common or foreign
 names or abbreviations as aliases for their subdivisions. These are defined in
@@ -845,6 +845,11 @@ All other default values are highlighted with bold:
      - Autonomous communities: AN, AR, AS, CB, CE, CL, CM, CN, CT, EX, GA, IB, MC, MD, ML, NC, PV, RI, VC
      - en_US, **es**, uk
      -
+   * - Sri Lanka
+     - LK
+     -
+     - en_US, **si_LK**, ta_LK
+     - BANK, GOVERNMENT, WORKDAY
    * - Sweden
      - SE
      -

holidays/calendars/__init__.py

@@ -22,4 +22,5 @@
 from holidays.calendars.julian import JULIAN_CALENDAR
 from holidays.calendars.julian_revised import JULIAN_REVISED_CALENDAR
 from holidays.calendars.persian import _Persian
+from holidays.calendars.sinhala import _SinhalaLunar, _CustomSinhalaHolidays
 from holidays.calendars.thai import _ThaiLunisolar, KHMER_CALENDAR, THAI_CALENDAR