Clarify PackedByteArray.decompress* limitations with external data

doc/classes/PackedByteArray.xml

@@ -174,6 +174,7 @@
 			<param index="1" name="compression_mode" type="int" default="0" />
 			<description>
 				Returns a new [PackedByteArray] with the data decompressed. Set [param buffer_size] to the size of the uncompressed data. Set the compression mode using one of [enum FileAccess.CompressionMode]'s constants.
+				[b]Note:[/b] Decompression is not guaranteed to work with data not compressed by Godot, for example if data compressed with the deflate compression mode lacks a checksum or header.
 			</description>
 		</method>
 		<method name="decompress_dynamic" qualifiers="const">
@@ -184,6 +185,7 @@
 				Returns a new [PackedByteArray] with the data decompressed. Set the compression mode using one of [enum FileAccess.CompressionMode]'s constants. [b]This method only accepts brotli, gzip, and deflate compression modes.[/b]
 				This method is potentially slower than [method decompress], as it may have to re-allocate its output buffer multiple times while decompressing, whereas [method decompress] knows it's output buffer size from the beginning.
 				GZIP has a maximal compression ratio of 1032:1, meaning it's very possible for a small compressed payload to decompress to a potentially very large output. To guard against this, you may provide a maximum size this function is allowed to allocate in bytes via [param max_output_size]. Passing -1 will allow for unbounded output. If any positive value is passed, and the decompression exceeds that amount in bytes, then an error will be returned.
+				[b]Note:[/b] Decompression is not guaranteed to work with data not compressed by Godot, for example if data compressed with the deflate compression mode lacks a checksum or header.
 			</description>
 		</method>
 		<method name="duplicate">