Added partial draft of grammar doc

grammar.txt

@@ -0,0 +1,33 @@
+expression ->
+	| literal
+//	| IDENTIFIER
+//	| sequence
+	| unary
+	| binary
+//	| let
+//	| when
+	| if
+	| variant
+	| record
+	| list
+	| field
+	| index
+	| grouping ;
+
+literal -> NUMBER | STRING ;
+grouping -> "(" expression ")" ;
+unary -> ( "-" | "!" ) expression ;
+binary -> expression operator expression ;
+operator ->
+	| "==" | "!=" | "<" | "<=" | ">" | ">="
+	| "+" | "-" | "*" | "/"
+	| "|>" | "<|" | ">>" | "<<"
+	| "++" ;
+if -> "if" expression "then" expression "else" expression ;
+variant -> "`" IDENTIFIER ( "(" ( expression ( "," expression)* )? ")" )? ;
+record ->
+	"{" ( IDENTIFIER "=" expression ( "," IDENTIFIER "=" expression )* )? "}" ;
+list -> "[" ( expression ( "," expression )* )? "]" ;
+field -> expression "." identifier ;
+index -> expression "[" expression "]" ;
+grouping -> "(" expression ")" ;