(Som) Add the structure and placeholders for Somali RG

src/somali/GrammarSom.gf

@@ -0,0 +1,20 @@
+concrete GrammarSom of Grammar =
+  NounSom,
+  VerbSom,
+  AdjectiveSom,
+  AdverbSom,
+  NumeralSom,
+  SentenceSom,
+  QuestionSom,
+  RelativeSom,
+  ConjunctionSom,
+  PhraseSom,
+  TextX - [Adv],
+  StructuralSom,
+  IdiomSom,
+  TenseX - [Adv]
+  ** {
+
+flags startcat = Phr ; unlexer = text ; lexer = text ;
+
+} ;