Added optional feature `copy`: Make `StackString<SIZE>` a `Copy` type.

Fortune for stack-str's current commit: Future curse − 末凶

Cargo.toml

@@ -5,4 +5,12 @@ edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
+[features]
+
+# Make `StackString<SIZE>` a `Copy` type
+#
+# This can be useful for small values of `SIZE`, but it will cause a lot of unneeded and redundant copying of large values of `SIZE`.
+# Therefore, it is avdised to only be enabled if using only small `StackString`s.
+copy = []
+
 [dependencies]