Update Sinhala orthography (#19288)

Patch from Harshula Jayasuriya.

fc-lang/si.orth

@@ -24,26 +24,49 @@
 #
 # Sinhala/Sinhalese (si)
 #
-# The glyph list is based on information available at:
+# The document SINHALA CHARACTER CODE FOR INFORMATION INTERCHANGE, PART 2:
+# REQUIREMENTS AND METHODS OF TEST (SLS 1134:PART2:2007 UDC 003.035:003.336)
+# describes three (3) levels of compliance for Unicode Sinhala fonts. The
+# first level describes the minimum requirements for SLS certification. The
+# third level includes the first and second level requirements and additional
+# requirements.
 #
-# http://std.dkuug.dk/JTC1/SC2/WG2/docs/n2737.pdf
+# To get a copy of this document contact the Sri Lanka Standards Institution
+# (http://www.slsi.lk/).
 #
-# and Unicode 5.0 Section 10.1.
+# The Unicode document: http://unicode.org/charts/PDF/U0D80.PDF
+# describes the base for level 3 compliance.
 #
+# Level 1 compliance can be described as level 3 with the exclusion of:
+# U+0D8F ILUYANNA (Independent Vowel)
+# U+0D90 ILUUYANNA (Independent Vowel)
+# U+0DDF GAYANUKITTA (Dependent Vowel)
+# U+0DF3 DIGA GAYANUKITTA (Dependent Vowel)
+# U+0DF4 KUNDDALIYA (Punctuation)
+#
+# Sinhala and SLS1134 experts can be contacted at:
+# sinhala-technical at lists.sourceforge.net
+# ltrl at ucsc.cmb.ac.lk
+#
+# Semi Consonants
 0d82-0d83
-0d85-0d8d
-#0d8e-0d90 are not in modern use (SLS 1134 p. 4)
+# Independent Vowels
+0d85-0d8e
+# 0d8f ILUYANNA (Level 3)
+# 0d90 ILUUYANNA (Level 3)
 0d91-0d96
-0d9a-0da5
-#0da6 is not in modern use (SLS 1134 p. 5)
-0da7-0db1
+# Consonants
+0d9a-0db1
 0db3-0dbb
 0dbd
 0dc0-0dc6
+# Dependent Vowels
 0dca
 0dcf-0dd4
 0dd6
-0dd8-0ddf
+0dd8-0dde
+# 0ddf GAYANUKITTA (Level 3)
 0df2
-#0df3 is not in modern use (SLS 1134 p. 6)
-#0df4 is historical punctuation (Unicode 5.0 pp. 342-343)
+# 0df3 DIGA GAYANUKITTA (Level 3)
+# Punctuation
+# 0df4 KUNDDALIYA (Level 3)