patch 8.2.2756: Vim9: blob index and slice not implemented yet

Problem:    Vim9: blob index and slice not implemented yet.
Solution:   Implement blob index and slice.
diff --git a/src/proto/blob.pro b/src/proto/blob.pro
index 3bc6625..6be7f0b 100644
--- a/src/proto/blob.pro
+++ b/src/proto/blob.pro
@@ -13,5 +13,6 @@
 int write_blob(FILE *fd, blob_T *blob);
 char_u *blob2string(blob_T *blob, char_u **tofree, char_u *numbuf);
 blob_T *string2blob(char_u *str);
+int blob_slice_or_index(blob_T *blob, int is_range, varnumber_T n1, varnumber_T n2, int exclusive, typval_T *rettv);
 void blob_remove(typval_T *argvars, typval_T *rettv);
 /* vim: set ft=c : */