Add comment about 'locals' queries limitations

This is not enough of an issue to avoid using the functionality however,
for example variable declarations are thankfully not affected by this
issue, since they *must* be declared before their use.

queries/locals.scm

@@ -1,3 +1,9 @@
+; See this issue [1] for support for "lazy scoping" which is somewhat needed
+; for Tiger semantics (e.g: one can call a function before it has been defined
+; top-to-bottom).
+;
+; [1]: https://github.com/tree-sitter/tree-sitter/issues/918
+
 ; Scopes {{{
 [
  (for_expression)