✨ sink: add SinkString::empty and SinkString::with_capacity

src/sink.rs

@@ -68,6 +68,18 @@ mod string_sink {
     pub struct SinkString(pub String);
 
     impl SinkString {
+        #[inline]
+        #[must_use]
+        pub fn empty() -> Self {
+            Self(String::new())
+        }
+
+        #[inline]
+        #[must_use]
+        pub fn with_capacity(capacity: usize) -> Self {
+            Self(String::with_capacity(capacity))
+        }
+
         #[inline]
         #[must_use]
         pub fn from_string_ref(s: &String) -> &Self {