deprecate the types as well

Author: giacomocavalieri

src/gleam/bytes_builder.gleam

@@ -24,6 +24,7 @@ import gleam/bit_array
 import gleam/list
 import gleam/string_builder.{type StringBuilder}
 
+@deprecated("The `bytes_builder` module has been deprecated, use the `bytes_tree.BytesTree` type instead.")
 pub opaque type BytesBuilder {
   Bytes(BitArray)
   Text(StringBuilder)

src/gleam/string_builder.gleam

@@ -16,6 +16,7 @@ import gleam/list
 /// performance by not using a string builder. Always benchmark your performance
 /// sensitive code.
 ///
+@deprecated("The `string_builder` module has been deprecated, use the `string_tree.StringTree` type instead.")
 pub type StringBuilder
 
 /// Create an empty `StringBuilder`. Useful as the start of a pipe chaining many