feat(api): add replace_keycodes to nvim_set_keymap (#19598)

src/nvim/buffer_defs.h

@@ -369,6 +369,7 @@ struct mapblock {
   char m_expr;                  // <expr> used, m_str is an expression
   sctx_T m_script_ctx;          // SCTX where map was defined
   char *m_desc;                 // description of keymap
+  bool m_replace_keycodes;      // replace termcodes in lua function
 };
 
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