patch 8.2.1826: Vim9: cannot use a {} block at script level

Problem:    Vim9: cannot use a {} block at script level.
Solution:   Recognize a {} block.
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index 0c83f52..0b52c11 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -1812,6 +1812,12 @@
 EXCMD(CMD_at,		"@",		ex_at,
 	EX_RANGE|EX_WHOLEFOLD|EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_LINES),
+EXCMD(CMD_block,	"{{{{{{{{",	ex_block,  // not found normally
+	0,
+	ADDR_NONE),
+EXCMD(CMD_endblock,	"}",		ex_endblock,
+	EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
+	ADDR_NONE),
 EXCMD(CMD_tilde,	"~",		ex_substitute,
 	EX_RANGE|EX_WHOLEFOLD|EX_EXTRA|EX_CMDWIN|EX_LOCK_OK|EX_MODIFY,
 	ADDR_LINES),