fix: scanner: make state_new() static (#17)

I suspect this is what causing issues for multiple projects attempting to use this grammar:

- neurocyte/zat#1

- zed-industries/zed#7543 (comment)

Don't know why it wasn't static in the first place (in the original Haskell grammar),
but I looked at what other grammars do and none export any functions other than those used by Tree-sitter.

src/scanner.c

@@ -215,7 +215,7 @@ typedef struct {
 #endif
 } State;
 
-State state_new(TSLexer *l, const bool * restrict vs, indent_vec *is) {
+static State state_new(TSLexer *l, const bool * restrict vs, indent_vec *is) {
   return (State) {
     .lexer = l,
     .symbols = vs,