formatter: add DATA_BLOCK to BLOCKS + DECLARATIONS

Without this, DATA_BLOCK wasn't recognized as a declaration block,
so the stack was never populated for DB files. END_DATA_BLOCK fell
through to regular-line handling and got a tab prefix (from body
get_indent()), while DATA_BLOCK itself was flush-left.

Added DATA_BLOCK to both BLOCKS (ender = END_DATA_BLOCK) and
DECLARATIONS so it gets the same treatment as FUNCTION_BLOCK:
stack cleared, no_indent=true, and END_DATA_BLOCK handled by the
declaration ender path (flush-left output).

src/formatter.lua

@@ -43,6 +43,7 @@ local BLOCKS = {
   ["FUNCTION"] = "END_FUNCTION",
   ["FUNCTION_BLOCK"] = "END_FUNCTION_BLOCK",
   ["ORGANIZATION_BLOCK"] = "END_ORGANIZATION_BLOCK",
+  ["DATA_BLOCK"] = "END_DATA_BLOCK",
   ["TYPE"] = "END_TYPE",
   ["STRUCT"] = "END_STRUCT",
   ["VAR"] = "END_VAR",
@@ -91,6 +92,7 @@ local DECLARATIONS = {
   ["FUNCTION"] = true,
   ["FUNCTION_BLOCK"] = true,
   ["ORGANIZATION_BLOCK"] = true,
+  ["DATA_BLOCK"] = true,
   ["TYPE"] = true,
   ["STRUCT"] = true,
 }