add else if, else, and comments

src/lexer/lex.l

@@ -47,6 +47,7 @@ int yywrap(void *) {
 
 
 "if"                { return TOKEN_IF; }
+"else if"              { return TOKEN_ELSE_IF; }
 "else"              { return TOKEN_ELSE; }
 "while"             { return TOKEN_WHILE; }
 "forever"           { return TOKEN_FOREVER; }
@@ -102,6 +103,8 @@ int yywrap(void *) {
     COLUMN_NO += yyleng;
 }
 
+#[^\n]* {}
+
 .   {
     GET_STATE
     fprintf(stderr, "%s:%u:%u error: unexpected character '%s'\n", state->path, yylineno, COLUMN_NO+1, yytext);

src/lexer/token.h

@@ -39,6 +39,7 @@ typedef enum {
 
   // Keywords
   TOKEN_IF,
+  TOKEN_ELSE_IF,
   TOKEN_ELSE,
   TOKEN_WHILE,
   TOKEN_FOREVER,