feat(grammar): add grammar file

grammar.ebnf

@@ -0,0 +1,31 @@
+token        ::= insert
+               | select
+               | meta-command
+               | int
+               | string
+               | end-of-file
+
+insert       ::= "insert"
+select       ::= "select"
+
+meta-command ::= "." "exit"
+
+int          ::= sign? digit+
+sign         ::= "+"
+               | "-"
+digit        ::= "0"
+               | "1"
+               | "2"
+               | "3"
+               | "4"
+               | "5"
+               | "6"
+               | "7"
+               | "8"
+               | "9"
+
+string       ::= '"' string-char* '"'
+string-char  ::= '\' utf8-char
+               | utf8-char-not-dbl-quote
+
+               

notes.org

@@ -224,7 +224,11 @@ i will use rustyline, since it seems like the most feature-complete
 
 * DONE print errors to stderr
 
-* TODO write a proper grammar
+* DONE write a proper grammar
+
+* TODO .about meta-command
+* TODO .version meta-command
+* TODO .license meta-command
 
 * TODO parse insert statements in the form
 insert <id:int> <username:string> <email:string>