include llama.cpp since there were some edits

llama.cpp/grammars/arithmetic.gbnf

@@ -0,0 +1,6 @@
+root  ::= (expr "=" ws term "\n")+
+expr  ::= term ([-+*/] term)*
+term  ::= ident | num | "(" ws expr ")" ws
+ident ::= [a-z] [a-z0-9_]* ws
+num   ::= [0-9]+ ws
+ws    ::= [ \t\n]*