no_std

Add `std` default feature
Only implement for String if `std` is enabled
Replace std Vec with heapless

src/traits.rs

@@ -13,6 +13,7 @@ impl AnsiParser for str {
     }
 }
 
+#[cfg(any(feature = "std", test))]
 impl AnsiParser for String {
     fn ansi_parse(&self) -> AnsiParseIterator<'_> {
         AnsiParseIterator {